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Ground Truth Studies Teacher Handbook - Aspen Global Change ...

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CHANGE INSTITUTEASPEN GLOBAL

Ground

Truth

Studies

Teacher Handbook

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

i


Printing History

First U.S. Edition

First Printing June 1992

Second Printing July 1993

Canadian Edition

First Printing June 1994

Second U.S. Edition

Third Printing June 1995

Forth Printing December 2000

Subsequent Printings by Print on Demand

© 1992, 1995, 2003 Aspen Global Change Institute

All rights reserved.

For reproduction in whole or part, obtain permission from the—

Aspen Global Change Institute

100 East Francis Street

Aspen, Colorado 81611

tel 970 925 7376

fax 970 925 7097

email agcimail@agci.org

homepage http://www.agci.org

Printed on 100% recycled paper using soy-based inks.


Contributing Authors

Jesse Boyce; Susan Hassol; John Katzenberger; Martha Kirpes; Anthony Leiserowitz; William Stapp.

Design and Production

Kelly Alford/Words Colors Pictures.

Acknowledgments

The GTS Teacher Handbook is a cross-disciplinary synthesis of the talents, skills and wisdom

of an international group of scientists and educators. A heartfelt thank-you to them all.

The Curriculum Development Team

Mr. Walter Bogan, AAAS; Dr. Cheryl Charles, Project WILD; Mr. Gregory Cox, University of Alabama/Huntsville;

Dr. William Kuhn, University of Michigan; Dr. James Lawless, NASA; Dr. Milton McClaren, Simon Fraser University;

Dr. William Stapp, University of Michigan; and Mr. Thomas Wagner, ERIM.

Pilot Teachers

Ms. Elaine Bonds, Aspen Elementary School, Aspen, CO; Ms. Vicki Clark, Mathematics & Science Center, Richmond, VA; Ms. Cheryl Cleeves,

Clifford Elementary School, Redwood City, CA; Ms. Debi Edwards, Academy for Science and Foreign Language, Richmond, VA; Mr. Chris Faison,

Aspen Community School, Aspen, CO; Ms. Pamela Favenisi, Sparkman High School, Toney, AL; Ms. Camarie Hull, Aspen Community School,

Aspen, CO; Mr. Patrick Lee, Clifford Elementary School, Redwood City, CA; Ms. Susan Lloyd, Academy for Science and Foreign Language,

Huntsville, AL; Ms. “Sam” Mitchell, Porter Middle School, Austin, TX; Mr. Mark Munger, Aspen Community School, Aspen, CO; Ms. Wilma

Parker, Lahser High School, Bloomfield Hills, MI; Ms. Angela Poleselli, Clifford Elementary School, Redwood City, CA; Mr. Gary Prosch, Jenison

Jr. High School, Jenison, MI; Ms. Karen Ross, Weber Jr. High School, Saginaw, MI; Mr. Don Ruecroft, Robious Middle School, Midlothian, VA;

Ms. Cheryl Shelton, Academy for Science and Foreign Language, Richmond, VA; Mr. Larry Smith, Sparkman High School, Toney, AL; Dr. Dennis

Travis, Lahser High School, Bloomfield Hills, MI; Dr. Miriam Turner, Renaissance High School, Detroit, MI

and Ms. Donna Ward, Aspen Elementary School, Aspen, CO.

Other Contributors

Mr. Jim Balcerski, ERIM; Ms. Sue Burcham, Mt. View Jr. High-Beaumont, Beaumont, CA; Dr. Hector D’Antoni, NASA; Ms. Martha Kirpes,

University of Michigan; Mr. Rod MacVicar, Centennial Senior Secondary, Coquitlam, BC, Canada; Mr. Sam Patalano; Ms. Shaelyn Raab; Ms.

Barbara Riedel, USGS; Mr. Bob Samples, Project WILD; Mr. Ed Sheffner, TGS Technologies; Ms. Janet van Mastrigt; Mr. Bob Whitney, Antelope

Valley High School, Lancaster, CA; the many global change scientists and environmental educators who volunteered hours of expertise during the

AGCI Summer Science Conferences, and Susan Hassol, the principal writer for the Handbook.

Funding

Initial funding and in-kind contributions for the Ground Truth Studies Teacher Handbook have been provided by the Amway Corporation, the

Consortium for International Earth Science Information Network (CIESIN), the Intergraph Corporation, NASA, EPA, The National Wildlife

Federation,

and the University of Alabama in Huntsville.

Comments Welcome

Ground Truth Studies is an ongoing curriculum development project. The GTS Teacher Handbook is revised periodically to incorporate

teacher evaluations and new approaches. We welcome your comments, criticisms, and suggestions about your experience using GTS

activities. Your evaluations will be reviewed each time the Teacher Handbook is revised.

Please send your comments to the Aspen Global Change Institute.


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Table of Contents

Acknowledgments

Preface

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/ vii

Introduction

Ground Truth Studies: Overview / 3

How to Use This Book / 5

Primers

Global Change Primer / 11

Remote Sensing Primer / 31

Activities

Activities By Grade Level / 37

Learning to Look, Looking to See / 39

Just Right: The Goldilocks Effect / 43

Where Are You From a Bird’s Eye View / 45

Sand Boxes and Satellites / 47

Digital Faces / 49

Zooming In / 53

Ground Truthing Your Image / 67

Investigating the Invisible / 71

How When Affects What: Part I / 73

How When Affects What: Part II / 75

How When Affects What: Part III / 83

Dust Busters / 85

Dead Right, Dead Wrong / 87

Back to the Future / 89

Map Your Watershed / 91

Land Cover Mapping / 93

A Changing Watershed / 97

Your Watershed’s Story / 101

Make a Watershed Model / 105

River Walk / 109

Regulatory Agencies on the River / 113

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Table of Contents (continued)

Appendices

Global Temperature Data Set / 119

Glossary / 121

Image Applications Chart / 131

Sources For Remote Sensing Imagery / 137

Suggested Reading and Resources / 141

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Preface

Ground Truth Studies is an interdisciplinary activity-based

program that draws on the broad range of sciences that

make up the study of global change and the complementary

technology of remote sensing. Satellite and aerial

imagery open a unique window onto the face of the Earth.

These images are inviting and, once they become familiar,

offer the learner — of any age — a new visual language

with direct relevance to local as well as global environmental

change. A key element of remote sensing is to go

out into the area covered by an image and make observations

and measurements. This direct observation or

“ground truthing” complements and verifies the remotelysensed

data, hence the title of this book. The Ground

Truth Studies Teacher Handbook provides supplementary

program material for use by both primary and secondary

teachers. The Handbook contains an introduction to global

change and remote sensing, a generic set of images, a set

of student activities, and reference materials.

Critical global change issues which are gaining recognition

in this decade — unprecedented biodiversity loss, climate

change, and stratospheric ozone depletion — will all

remain center stage as we enter the 21st century. A clear

and necessary educational challenge is to face these issues

with the information to make wise decisions. These issues

are rich in the fundamentals of science. Educational

approaches which build on the strength of an individual

discipline such as biology, while at the same time fostering

the integration across disciplines, are required for gaining a

grasp of the complex new field of study described as Earth

system science. How people interact with the process of

global change is not only fascinating, it is becoming

central to how we chart our future as a species.

The aim of the GTS Teacher Handbook is to explore these

global change issues with the aid of the powerful tool of

remote sensing. The National Aeronautics and Space

Administration describes the role remote sensing will play

in gaining new knowledge of how Earth systems work as

“Mission to Planet Earth.” The range, quantity, and

complexity of satellite data require a new commitment to

its interpretation and use. The knowledge gained is a

critical piece of the puzzle of our dynamic planet and lays

the foundation for the development of global environmental

policy, such as the international accord for CFC

regulation. It can also serve as a guide for making

personal decisions that impact one's local environment

and, ultimately, the global environment.

The 20th century is perhaps the last century humanity will

view the Earth as an infinite expanse from which to

appropriate the necessary resources for supporting human

activity. What we do, from clearing forest cover to

growing rice to burning fossil fuels to manufacturing and

transporting goods, transforms essential elements of the

biosphere. Where are the models to guide us toward a

sustainable use of resources in the 21st century? What

tools do we have to mitigate our global impacts or to

approach whole ecosystems wisely? What is required to

approach these questions with even tentative confidence?

The challenge of this decade is to assemble the data, the

ideas, and the models that transcend the limits of singledisciplinary

research and forge new modes of crossdisciplinary

research. The educational challenge is to

provide approaches that embrace the natural and social

sciences, and provide the basis for policy and practice that

is sensitive to the immediate and long-term needs of our

complex, miraculous home planet.

The study of global change is as close as your backyard or

school grounds. This Handbook is an invitation to link

local environmental conditions to the broader topics of

global change.

John Katzenberger

Aspen, Colorado

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Introduction

• GTS Overview

• How to Use This Book

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Ground Truth Studies

Overview

Ground Truth Studies (GTS) is a K-12, activity based,

science education program that integrates local environmental

issues with global change topics, such as the

greenhouse effect, loss of biological diversity, and ozone

depletion. GTS activities use aerial and satellite imagery

of the Earth as a powerful tool for learning about local,

regional and global environmental topics.

Ground Truth refers to the use of field measurements to

validate remotely sensed data. Field trips and classroom

activities demonstrate the need for ground truthing when

using remotely sensed images for environmental studies.

Student activities illustrate the use of the synoptic, or

“bird’s eye” view for recognizing patterns in Earth

systems and changes in patterns over time, such as urban

growth or deforestation. The activities are interdisciplinary

and integrate basic science and math skills with other

disciplines such as geography, social studies, art and

writing to address critical issues in local and global

environmental change.

Ground Truth Studies Key Concepts

Change is the norm for the Earth’s natural systems

• Recently, humans have become a key agent of change

• Earth systems are linked through interactive processes

Global change impacts all life

• Local changes have global consequences

Ground Truth Studies and

Mission to Planet Earth

Mission to Planet Earth is an initiative to understand our

home planet, how forces shape and affect its environment,

how that environment is changing, and how those

changes will affect us.

—Dr. Sally K. Ride

Over the next 20 years, the dominant source of data

about the global environment will come from space

observations in which the Earth’s land, oceans, and

atmosphere will be measured by remote sensing from a

network of satellites. Mission to Planet Earth is the

central NASA contribution to the US Global Change

Research Program. Mission to Planet Earth involves

government agencies and the research community in an

exciting and challenging task with enormous social

consequences.

Each satellite image requires interpretation to be of value

to researchers, educators, students, policy makers —

anyone interested in the state of the planet. Learning how

to interpret remotely sensed images is like learning a

new language — a visual language vital for understanding

Earth Systems

Ground Truth Studies is designed to introduce remote

sensing as an exciting tool at the elementary and

secondary levels. By utilizing remotely sensed images of

their own region, students gain new skills and insights

into local environmental issues and global change topics.

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GTS Overview (continued)

Ties to Basic Science

Global change is rich in its range of topics from both

the natural and social sciences. Since all Earth systems

are interrelated, global change science requires perhaps

the greatest integration of disciplines ever undertaken.

Chemistry, physics, ecology, geology, sociology,

economics and ethics are just a few of the disciplines

involved. Students experience this interplay of subjects

and learn essential skills, such as collecting, graphing

and interpreting data, which are vital to the process of

exploring their own environment. Student observations

and measurements are linked to global change topics.

GTS Activities are interdisciplinary and help to

reinforce core curricular objectives and complement the

aim of the science content standards developed in the

draft National Science Education Standards.

The Ground Truth Studies

Teacher Handbook

This handbook is designed to supplement existing curricula

and has been used successfully at all age levels. It is

available to elementary and secondary teachers either

directly or through AGCI workshops. Teacher support

materials such as remotely sensed images, educational

videos, or related information on teaching about global

change are available from the Aspen Global Change

Institute.

About the Aspen Global

Change Institute

AGCI was founded in 1989. Its mission is to further global

change science and to develop educational materials about

global change. Since 1990 AGCI has convened international

groups of scientists from both the natural and social

sciences for in-depth two-week sessions on current topics in

global change research. The GTS Teacher Handbook is the

first project of AGCI’s educational program and was part of

the educational activities of the International Space Year.

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How to Use This Book

There are many approaches to learning about global

change and any attempt to categorize global change is

difficult because Earth systems are so interrelated. The

air we breathe is intricately affected by processes

occurring simultaneously in the atmosphere, water,

land and life on Earth. This handbook is the first in a

series that will examine the issue of global change from

the perspective of four familiar, important and interrelated

Earth systems: air, water, land and living things.

It is important to develop the flexibility to step back

and view complex Earth systems as one immense

whole, as well as to delve into its parts. This notion of

viewpoint, or perspective, is essential to the study of

global change. For example, Earth, observed from the

surface of the moon, provides a global perspective

while the Earth observed from the edge of a pond,

provides a local view which is equally necessary to our

understanding of Earth systems. The activities in this

handbook address both of these perspectives through

the use of remotely sensed images that give a synoptic,

or bird’s eye view, and through ground truthing field

trips and activities to obtain a detailed view of our

planet.

Many issues, such as global warming, the ozone hole

and the loss of biological diversity, will be familiar to

you and your students, but the details of the role of

humans in causing global scale change will not be so

clear. As educators, we need to engage students in an

exploration of changing Earth systems and the role

humans play in some of those changes. Your students

will be keenly interested because it is their future which

is at stake. Global Change Studies are exciting because

of the linkages they forge between a multitude of

disciplines, and this Handbook is designed to provide

you with relevant activities to supplement your courses.

Background Information —

The Primers

To aid you in teaching about global change, we have

provided a Global Change Primer which answers many

frequently asked questions about a number of major global

change topics. This will give you a head start on many

global change issues, enable you to interpret the discussions

and events covered by the media, and provide you with

answers for many of the questions of your students.

This handbook uses remotely sensed images and ground

truthing activities to provide both large scale perspectives

and tools for the study of global change in the area where

you and your students live. The Remote Sensing Primer

provides an overview of the theory and application of

remote sensing technology. The bibliography lists a number

of excellent references on remote sensing that also include

striking images and case studies in the application of remote

sensing.

Remote sensing and ground truthing make use of the

knowledge and skills students acquire from many traditional

school subjects. These activities also remove the physical

walls between students and their environment. Their

improved ability to “see” and experience their world can

bring them closer to understanding the interdependence of

all life and the fragile systems of this complex planet, Earth.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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How To Use This Book (continued)

Instructional Framework

The instructional framework of this handbook is

constructed using three levels of activities:

Tool box — activities designed to explore and develop

essential skills and concepts for field observation,

measurement, etc. These activities also provide an

orientation to important components of the local

environment.

Local and regional issues — activities designed to

develop the student’s understanding of what we know

about Earth Systems, and how we know. These

activities develop and apply the basic “toolbox” skills

by combining the interpretation of remotely sensed

images of the Earth with ground truth activities for

studying the local environment. Field observation

complemented with remotely sensed image interpretation

leads to a better understanding of local and

regional environmental issues.

Global Change: The big picture — activities that are

aimed at integrating the skills, concepts and observations

developed in the preceding activities in ways that

increase the student’s understanding of how local scale

environment relates to regional and global scale Earth

systems. Students will learn how the actions of

individuals and communities add up to regional and

global effects and how an individual’s vision can help

shape the Earth of the future.

As the first handbook in this series, there is an emphasis

on the toolbox activities, but there are also extensions to

lead you and your students far beyond the limits of the

local school yard. The satellite images contained within

this handbook, and others available through your library

or other local sources, provide an excellent resource for

stepping back from our usual up-close view and adopting a

global perspective. To fully utilize the activities in this

handbook, we highly recommend that each school develop a

set of local images. For assistance, please contact AGCI, or

consult the Sources for Remote Sensing Imagery located in

the appendices.

Suggestions for K

through 6 Grade Teachers

Many of the activities in this handbook are well suited for

students as young as Kindergarten. The younger children

(grades K—3) will gain the most from the hands-on and

visually and sensory oriented activities, such as “Learning to

Look, Looking to See”, “Goldilocks Effect”, “Birds Eye

View” and “Sandboxes and Satellites”. You should feel free,

however, to adapt any of the activities to fit topics you are

covering in your classes. The remotely sensed images

fascinate young and old alike, and the opportunity to trace

the route home or around school, using an aerial image,

provides a powerful learning experience.

Ground Truth Studies is designed as a hands-on, interdisciplinary

program. The activities are equally applicable to art,

science, math and writing classes, and your students will

learn most effectively from hands-on involvement in these

activities. Building models, tracing features on acetate over

the aerial images, and taking field trips to “ground truth” the

images are essential elements of Ground Truth Studies. Look

over all of the activities offered in this handbook for only you

can judge the level of your students and determine how these

activities can be used to supplement your class work.

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How To Use This Book (continued)

To build a foundation for their future classes, encourage

your students from the beginning to record their

observations and thoughts in writing or pictures, to

count the numbers of objects rather than classify them

as a few, many or a lot and to verbalize what they have

learned by writing stories, poems or songs. Students too

young to write can report orally, or they can build

models, draw or paint pictures to express what they

have learned. Give your students the opportunity to

complete their learning experience by letting them teach

their classmates what they have learned.

Suggestions for 7

through 12 Grade Teachers

The suggestions for primary teachers certainly hold true

at the secondary level. All of the activities in this

handbook should also be considered for use with

secondary level students. Experience has shown that

older students have much to gain by carrying out the

activities suggested for younger class levels.

At the secondary level specialization intensifies and

math, science, geography, language and art classes are

usually taught as distinct disciplines. Ground Truth

Studies strives to bridge the divisions between subjects

while respecting the needs of teachers to cover their

assigned material. The GTS activities provide compelling

and relevant materials to engage students and to

carry their lessons beyond any given discipline.

• Science and math classes may monitor the local environment

by identifying, classifying and measuring different

variables such as temperature, dust, plant cover, and

urbanization. Students will then tabulate, map, graph and

report their results with explanations of their findings.

• Geology classes can trace watersheds, map rock outcrops

and features of the area on the remotely sensed images,

and take field trips to ground truth their interpretation of

the image.

• Geography classes can use the aerial images to make their

own map and compare it with other maps of the same

area.

• Social studies, history and language classes can research

and report on the history of their watershed, look at the

past and speculate about the future of their community,

and look at the role of regulatory agencies in the community.

• Theater classes can research and enact an activity such as

“Your Watershed’s Story”.

• Debate teams can use the materials “Regulatory Agencies

on the River” or “Dead Right, Dead Wrong” for relevant,

topical debates.

The list is extensive and rich in materials from which to

weave basic natural and social science themes:

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How To Use This Book (continued)

Appendices

The appendices include a temperature data set, glossary, two

sections on remote sensing, and a bibliography.

The Global Temperature Data Set is for use with the

“How When Affects What” set of activities and provides

one set of data used by scientists when conducting research

on global climate change.

The Glossary supplies standard definitions of terminology

found in the primers or activities. Scanning through it

beforehand may help you avoid problems with some of the

inevitable jargon and specialized terminology.

The next two appendices supply additional information on

remote sensing applications. The Image Application Chart

is inevitably incomplete as remote sensing is constantly

being applied to new applications across the entire range of

disciplines from archaeology to zoology. The appendix,

Sources of Remote Sensing Imagery, provides a list of

sources for remotely sensed images.

Finally, a short Bibliography contains both background

information and further reading on remote sensing and

global change. Some useful webpages including AGCI are

listed. If your favorite book or article on the topic is

missing, please let us know!

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Primers

Global Change Primer

• Remote Sensing Primer

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Global Change Primer

These are unique times. Our use of energy and other resources has increased to the point where we are having a measurable

effect of a global scale on Earth systems such as the atmosphere. Humans have moved from mere spectators of

Earth processes to center stage in the twentieth century, where we have become major players. It is no accident that we

are hearing about many different global change issues all at once: climate change, the ozone hole and worldwide loss of

biodiversity, just to name a few. It is, in fact, because we humans have become so numerous and consumptive, that our

combined individual effects are precipitating changes on a global scale. A number of key concepts are central to the

scientific study of global change and help put the issue of natural and human induced global change into perspective.

Change is the norm for Earth’s natural systems

The Earth is constantly changing. Some of this change occurs slowly over many millennia, and some occurs relatively

rapidly over decades. Major natural forces cause such changes as volcanoes, continental shifts, building and erosion of

mountains, reorganization of oceans, appearance and disappearance of deserts and marshlands, advances and retreats of

great ice sheets, rise and fall of sea and lake levels, and the evolution and extinction of vast numbers of species.

Recently, human beings have become a key agent of change

In addition to the changes brought about by natural forces, it has recently become apparent that a relative newcomer to

planet Earth — the human being — has become a powerful agent of environmental change. The chemistry of the

atmosphere has been significantly altered by the agricultural and industrial revolutions. The erosion of continents and the

sedimentation of rivers and shorelines has been accelerated by construction, agriculture, and other human activities. The

production and release of toxic chemicals has affected the health and distribution of plant and animal populations. The

development of water resources for human use has affected patterns of natural water exchange in the hydrologic cycle

(e.g., enhanced evaporation from reservoirs and irrigation as compared to that from unregulated rivers). As human

population grows and technology develops, the role of human beings as agents of global change will undoubtedly

expand.

Earth’s systems are linked through interactive processes

Evidence accumulated in the last two decades indicates that environmental changes are the result of complex interactions

between natural and human-related systems. For example, the Earth’s climate changes are due not only to wind and

clouds in the atmosphere, but also the effects of ocean currents, human influences on atmospheric chemistry, the Earth’s

orbit and albedo, the Sun’s energy output, and the distribution of water between the atmosphere, hydrosphere (oceans,

lakes, rivers), and cryosphere (icecaps, glaciers, sea ice). The aggregate of these interactive linkages among the major

systems that affect the environment is known as Global Change.

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A Global Change Primer (continued)

Global Change impacts all life

Many environmental changes have substantial impacts on the welfare of humans and all other life on the planet—such as

changing growing seasons, extreme climatic events like protracted droughts, and increased exposure to damaging

ultraviolet radiation. During most of human existence, the only response to such changes was to learn to cope by building

better shelters, altering agricultural practices, or migrating. Advances in Earth sciences over the last several decades,

however, have revealed: 1) the causes of some changes, 2) the processes whereby they occur, and 3) their local environmental

consequences (although it remains difficult to prove precise cause and effect relationships between global activity

and local consequences). As a result of what we learn from Earth sciences, people can now anticipate some of these

changes and make proactive rather than reactive decisions and responses which can reduce the severity of Global Change

impacts and mitigate their effect.

Local changes have global consequences

It is increasingly clear that the cumulative effect of individual human activities is precipitating profound change on a

global scale. As a corollary, it also follows that individual actions can have an equally profound effect on the reduction

of detrimental human impacts on the Earth. Through awareness, education and informed action, the human race has the

opportunity to seize the initiative and avert, rather than adapt to or endure, an environmental crisis.

Thus, scientists are seeking to develop an integrated systems understanding of changes that relate to the welfare of the

entire planet. Such an understanding could greatly assist policy makers as they grapple with how to mitigate the impacts

of the key global change phenomena of our time: global climate change, stratospheric ozone depletion, acid deposition,

loss of biological diversity and changes in human population.

What are the key elements of Global Change research?

Shortly after the U. S. Global Change Research Program became organized it defined the large issue of Global Change

research into seven interdisciplinary science elements (in priority order) for the purpose of allocating the funding of

global change research:

1 Climate and Hydrologic Systems

This incorporates the atmospheric, oceanic, and land surface processes that govern atmospheric and oceanic circulations

and the associated distributions of temperature, moisture, clouds and precipitation over the surface of the Earth.

Key sub-elements include: the role of clouds in the Earth’s heat budget, greenhouse warming, sea level rise, water

supplies and stratospheric ozone depletion.

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A Global Change Primer (continued)

2 Biogeochemical Dynamics

An essential part of reliably predicting change on a global scale is an adequate understanding of the cycling of the

key nutrient elements — carbon, nitrogen, oxygen, sulfur, and phosphorous — through their major reservoirs: the

oceanic and freshwater aquatic systems, the solid Earth component, the biosphere, and the atmosphere. Subelements

include: greenhouse warming, acid deposition, deforestation, coastal pollution, and ozone depletion.

3 Ecological Systems and Dynamics

These are important to global change as both cause and effect. Ecosystems provide food and fiber for humans and

wildlife. They also influence air and water quality, the amount and distribution of surface and ground water, and the

habitats of both human and wildlife. Therefore, ecosystem destruction has direct effects on our economic and social

well-being. Variables such as temperature, precipitation, and biotic interactions ultimately control the distribution of

species. Species, in turn, influence the characteristics of ecosystems, and ecosystems influence the physical environment

through such phenomena as reflectance, evapotranspiration, and the emissions of important greenhouse gases,

such as carbon dioxide and methane. Therefore, ecosystems with altered structural and functional properties can

have feedback effects on the physical and chemical environment. Sub-elements include: biodiversity, coastal

pollution, sea level rise, erosion, ozone depletion, greenhouse warming, and acid deposition.

4 Earth System History

The Earth’s geologic record provides a valuable source of information about past changes in climate, ecosystems,

hydrologic conditions, and landscapes. Evidence of major variations in sea level, lake and ground water levels,

extent of glacier ice and sea ice, changes in atmospheric composition, and dramatic changes in ecosystems in the past

provide us with important insights into what the future may hold. We learn about natural climate variability by

indicators such as tree rings, ice cores, fossils, and sediment. Information about the causes, rates, and consequences

of climate change can also be extracted from the geologic record. Such information can improve our ability to make

predictions about future climate change.

5 Human Interactions

Human activity is a critical element in global change, both in terms of initiating processes of change, as well as

altering ongoing processes. Research into the human dimensions of global change will help us to understand the

patterns of direct human action or impact, as well as the indirect structural and institutional causes of change in Earth

systems, including such factors as economic markets, national legal and regulatory systems, and social and economic

aspirations of various nations. Such research will provide the scientific background for public policy studies, which

should address the response of human institutions to global change in terms of both mitigation strategies and

processes of adaptation.

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A Global Change Primer (continued)

6 Solid Earth Processes

Surface and sub-surface processes which produce changes on land, in the oceans, and in the atmosphere, are processes

studied under this research heading. Understanding solid earth processes is key in long-term planning in coastal

regions most at risk from rising sea levels or volcanic eruptions. Examples of solid earth processes are; melting of

glaciers and the effect on sea-level; volcanic eruptions (such as Mt. Pinatubo in 1991) and their effect on climate; and

rate of methane release from permafrost and gas hydrates as a potential positive feedback to the climate system.

7Solar Influences

The most well-known, explainable climatic variations, the Ice Ages, were caused by small variations in the solar

forcing of the terrestrial atmosphere due to small changes in the Earth’s orbit about the sun. A significant issue in

global change is in solar output variability and activity, and the understanding of the effect these have on the chemistry

and energy dynamics of the terrestrial atmosphere. Such understanding will help in modeling the type of climate

anomalies we can expect and the role of the Sun in these anomalies.

There are many ways to divide or categorize global change. While the above seven categories are useful for the purpose

of investigating what is not known or well understood about global change, less technical categories are useful for

primary and secondary education. We have approached the issue of global change from the perspective of four familiar,

important and interrelated Earth systems: air, water, land, and living things. Any attempt to categorize global change

themes is limited, because global change topics are so interrelated: The air we breathe is intricately related to processes

occurring in the atmosphere, water, land, and, of course, in the ecology of Earth, of which we are an essential part. It is

also important to step back and view complex Earth systems as one immense whole, as well as to explore the parts. This

notion of viewpoint, viewing the Earth from the surface of the moon, for example, provides only one data set. The view

of the Earth from a point on the edge of a pond provides an equally essential view. This Handbook explores....

The changing atmosphere

Along with widespread popular concern over such global change issues as global warming and ozone depletion, there are

equally widespread misconceptions. While these issues are only part of the global change arena, the attention given them

in the popular media and in political and environmental discussions warrants that they be specifically dealt with. This

section will attempt to offer a simple but accurate understanding of these phenomena, and clear up some of the confusion.

The concern about these issues centers around human induced, or anthropogenic change to the atmosphere. Thus, it is

important to review the basics of the Earth’s atmosphere in order to place human influences in their proper context.

The atmosphere is the gaseous envelope that supports life on Earth by providing chemicals necessary for life, protecting

the Earth’s inhabitants from harmful solar radiation, and acting as a transport mechanism for heat, moisture and essential

chemicals throughout the climate system. Through many complex processes, the atmosphere provides us with a comfortable

environment for life.

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A Global Change Primer (continued)

The structure of the

Earth’s atmospher e

Atmospheric scientists commonly divide

the atmosphere into four layers, or regions,

on the basis of the vertical distribution of

temperature (figure 1). Conditions vary

greatly over this large altitude range in

which the pressure and density decrease by

7 orders of magnitude (from about 1,000

millibars (mb) of pressure at the Earth’s

surface to 0.0001 mb at the top of the

thermosphere). The layers of the atmosphere

which concern us here are the two

layers closest to the Earth’s surface, the

troposphere and the stratosphere, which

extend from the Earth’s surface to an

altitude of about 50 km (30 miles).

The troposphere

The region nearest the Earth’s surface, the

troposphere, is the region in contact with

the biosphere. It is the region in which we

live and into which the gaseous byproducts

of our activities are released. It

is characterized by a decrease of temperature

with increasing altitude. The major

heat source for the lower atmosphere is the

absorption of solar energy by the surface

of the Earth. This heat is then transferred

to the atmosphere by a variety of processes

and contained there by the “greenhouse

effect”. This is the region where

almost all weather and clouds occur,

although vigorous convective systems,

like thunderstorms, can push through the

PRESSURE (mb)

0.0001

0.001

0.01

0.1

1

10

100

1000

THERMOSPHERE

MESOPAUSE

MESOSPHERE

STRATOPAUSE

STRATOSPHERE

TROPOPAUSE

TROPOSPHERE

CUMULONIMBUS

upper boundary and reach the lower stratosphere. The troposphere extends upward to approximately 6 to 8 km (4 to 5

miles) at the poles and about 17 km (11 miles) at the Equator. Air thins quickly as one goes up in altitude and breathing

OZONE

REGION

(mi)

60

50

40

30

20

CIRRUS

10

MT. EVEREST

8.8 km

180 190 200 210 220 230 240 250 260 270 280 290 300 degrees K

32

-140 -120 -100 -80 -60 -40 -20 0 20 40 60 80

TEMPERATURE

degrees F

Figure 1

Plot of vertical temperature distribution in the Earth’s atmosphere from

the surface to 100 km in altitude, giving the names of the atmospheric

regions. For comparison, the heights of high clouds and Mt. Everest are

also shown. (Adapted from: From Pattern to Process: The Strategy of the

Earth Observing System, vol. II, NASA)

100

90

80

70

60

50

40

30

20

10

GEOMETRIC HEIGHT (km)

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

15


A Global Change Primer (continued)

becomes difficult for humans above about 5 km (3 miles). Mount Everest reaches an altitude of just over 8.8 km (5.5

miles). The boundary zone between the upper troposphere and the lower stratosphere is the tropopause.

The stratosphere

The stratosphere is distinguished from the troposphere by the fact that its temperature remains nearly constant or

increases with increasing altitude to its upper boundary (the stratopause) at about 50 km (30 miles). After entering the

mesosphere, temperatures again begin to decrease with height. In the stratosphere, solar ultraviolet radiation causes

some molecular oxygen (O 2

) to dissociate, and the resulting atomic oxygen (O) then combines with the remaining O 2

to

form ozone (O 3

). The relatively higher concentration of stratospheric ozone is of critical importance because it absorbs

much, though not all, of the ultraviolet radiation at shorter wavelengths (80 to 90% of UV-B is absorbed by the atmosphere

under clear conditions, with almost no UV-B reaching the ground under heavily clouded skies) preventing it from

reaching the Earth’s surface, where excessive amounts are harmful to plant and animal life.

Past to present atmosphere

The gases of Earth’s atmosphere have changed dramatically since the formation of the Earth 4.6 billion years ago. The

early atmosphere consisted primarily of hydrogen which was poorly held by Earth’s gravity and escaped to space.

Heavier gases were released from the crust and an atmosphere consisting of nitrogen, ammonia, carbon monoxide,

hydrogen sulfide, and methane formed. Water vapor escaping from the crust condensed and formed the oceans. Energy

sources such as ultraviolet light, lightning, radioactive decay, and geothermal energy contributed to the formation of the

first organic molecules, eventually leading to early forms of life. After about 2 billion years, the presence of oxygen in

the atmosphere emerged as a byproduct of photosynthesis. Between two and three billion years after the Earth’s

formation, the buildup of oxygen from photosynthesis led to the development of ozone in the upper atmosphere, protecting

life from ultraviolet radiation. The presence of a strong component of oxygen in the atmosphere sets the Earth apart

from all the other planets in the solar system and is vital to life as it has evolved.

The primary dry air gases of the present atmosphere are nitrogen (N 2

) making up 78.1%, oxygen (O 2

) contributing

20.9%, and Argon (A) at 0.9%. The remaining gases are present in trace amounts totaling about 0.1%.

Trace gases

Not all trace gases are greenhouse gases, some trace gases have both natural and anthropogenic sources like carbon

dioxide (CO 2

) and methane (CH 4

), and some trace gases are only anthropogenic like the chlorofluorocarbons (CFCs).

Some trace gases are fairly stable and well mixed in the atmosphere such as the remaining “noble” gases like neon, while

others, such as water vapor (H 2

O), varies in concentration between 0 and 4%, and in distribution. Another gas that is

poorly mixed in the atmosphere is sulfur dioxide (SO 2

) which varies between 0.3 and 50ppbv (parts per billion by

volume). Sources of sulfur emissions into the atmosphere are a combination of natural processes such as volcanic and

biological activity (ocean organisms giving off dimethyl sulfide — DMS), and anthropogenic processes such as the

combustion of fossil fuels with sulfur content.

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A Global Change Primer (continued)

A striking example of a natural change in SO 2

was the eruption on June 15, 1991 of Mt. Pinatubo in the Philippines

which injected an estimated 20 Tg of SO 2

(a teragram is a trillion grams) into the stratosphere which was then converted

into sulfuric acid/water aerosols (sulfate aerosols). A satellite sensor tracked the distribution of the sulfate aerosol from

the point source at Mt. Pinatubo to a haze that circled the globe in 22 days and is thought to have lowered global average

temperatures by approximately 0.5 degrees C . Fortunately sulfur dioxide is not long-lived in the atmosphere. Two and

one-half years after the eruption, the amount of sulfur dioxide in the stratosphere from Mt. Pinatubo was estimated to

have decreased to 5 Tg. The estimate for emissions of SO 2

from all natural sources is 147 Tg per year however, emissions

from humans burning fossil fuels is estimated at 80 Tg per year, 4 times the amount from Mt. Pinatubo!

As the Mt. Pinatubo example illustrates, sulfur dioxide is a radiatively important trace gas, but not a greenhouse gas

because it has a cooling effect by reflecting incoming solar radiation back to space. The example of sulfur dioxide from

Mt. Pinatubo is one of rapid change with temporary effects from a natural source. The human caused release of sulfur

dioxide is one of a gradually increasing and continuous effect with a magnitude on a par with the natural system — a

definite example of global change. Since SO 2

has a short lifetime in the atmosphere the effects of decreasing emission

rates from anthropogenic sources are realized soon after the rates are changed.

Greenhouse gases

Another set of trace gases, that like sulfur dioxide are radiatively important, are the greenhouse gases. Unlike sulfur

dioxide however, the greenhouse gases are important in that they are mostly transparent to incoming solar radiation and

opaque to outgoing longwave radiation (figure 2). This trapping of energy is commonly called the “greenhouse effect,”

the basic physics of which has been understood since the last century as described in a paper by the Nobel Prize winning

chemist, Svante Arrhenius in 1896. This small group of gases has the remarkable effect of keeping the Earth about 33

degrees Celsius warmer than the moon, our cold and lifeless neighbor that receives the same amount of energy from the

sun. Concern is not with the greenhouse effect or the naturally occurring greenhouse gases. The concern is with the

additional greenhouse gases that have been added in increasing amounts this century creating an enhanced greenhouse

effect with as yet unknown consequences.

The greenhouse gases include water vapor, carbon dioxide (CO 2

), tropospheric ozone (O 3

), nitrous oxide (N 2

O),

chloroflurocarbons (CFCs), and methane (CH 4

). Anthropogenically important greenhouse gases are depicted in Figure 3.

Greenhouse gases trap incoming solar radiation and contribute to the warming of the Earth’s average temperature. In

addition to changes in temperature, there are other important aspects of the climate system that may respond to increased

concentration of greenhouse gases and the cooling effect of gases like sulfur dioxide. Examples of other potential

changes in climate are altered precipitation patterns, wind intensity and direction, frequency and severity of droughts,

and tropical storm formation and intensity.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

17


A Global Change Primer (continued)

Carbon

Nitrous

Dioxide Methane CFC-11 CFC-12 Oxide

Atmospheric concentration ppmv ppmv pptv pptv ppbv

Pre-industrial (1750-1800) 280 0.8 0 0 288

Present day 355 1.72 254 453 310

Current rate of change per year 1.8 0.015 9-10 17-18 0.8

(0.5%) (0.9%) (4%) (4%) (0.25%)

Atmospheric lifetime (years) (50-200) 10 65 130 150

ppmv = parts per million by volume; ppbv = parts per billion (thousand million) by volume; pptv = parts per trillion

(million million) by volume (Adapted from IPCC Scientific Assessment, 1990, and the 1992 IPCC Supplement)

Carbon dioxide

In relation to climate change, the most significant of the greenhouse gases is carbon dioxide, which has increased from

about 280 ppmv (parts per million by volume) during the pre-industrial period of 1750 to 1800 to the present day value of

356 ppmv (1993) primarily due to human combustion of fossil fuels and deforestation. This represents an increase of

about 25% in the past 100 years. Since 1958, measurements made at Mauna Loa, Hawaii by Charles David Keeling

Space

Incoming

Outgoing radiation

solar radiation Shortwave Longwave

{

{

8 17 6 9 40 20

Atmosphere

Absorbed by water

vapor, dust 0 3

4

19

Absorbed by clouds

Absorbed

Backscattered

by air

Reflected

by clouds

Reflected

by surface

Longwave

radiation

Net emission

by water vapor, CO 2

, O 3

Absorption by clouds,

water vapor, CO 2

, O 3

106

Emission

by clouds

Latent

heat flux

Sensible

heat flux

Ocean, land

46 115 100 7 24

Figure 2

Schematic diagram of the global average energy balance. The units are percent of incoming solar radiation. The solar energy absorbed at the

Earth’s surface directly heats the atmosphere and evaporates moisture. Atmospheric emission of infrared radiation back towards the Earth is

more than twice as large as the amount of solar radiation absorbed at the surface. This greenhouse energy permits the surface to warm

significantly more than would be possible by the solar radiation alone. (Adapted from MacCracken , M. C. and F. M. Luther (Eds.) Projecting

the Climatic Effects of Increasing Carbon Dioxide (1985), DOE/ER-0237, US Department of Energy, Washington, D.C.)

18

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


A Global Change Primer (continued)

provided for the first time accurate data on the increasing concentration of carbon dioxide, a sign of measurable human

impact on the Earth’s system (figure 4) at a global scale.

What about carbon dioxide concentration in the past? Did it go up and down with the changes in global temperature

coincident with the on-and-off cycles of the ice ages? Analysis of air bubbles trapped in ice cores at the Vostok research

station in Antarctica shows the fluctuation of carbon dioxide back in time 160,000 years (figure 5). The concentration of

CO 2

closely correlates with estimates of the Antarctic temperatures during the same time. As the temperature went down,

so did the concentration of CO 2

, and as it went up, so did CO . This does not provide a cause and effect relationship;

2

however it provides critical data relevant to understanding changes in climate with levels of CO 2

higher than at any time

in the last 160 thousand years.

Just how much CO 2

will there be in the atmosphere in the next century? The Intergovernmental Panel on Climate Change

(IPCC) future carbon emissions scenarios range from emissions lower than today’s, to emissions that are as much as 6

times greater than today’s. These scenarios are based on estimates of change in human population, economic growth,

and the relationship between economic growth and energy obtained from different sources. Today, emissions are about

6.2 GtC (gigatons or billion metric tons) of carbon per year.

Concentration of a gas in the atmosphere is only part of the story. The rate of change is of equal importance. CO 2

has

been increasing at a rate of approximately 0.5% per year which has lead the nations of the world to focus attention on

carbon emissions. While there is little dispute about the amount or sources of carbon emissions, there is uncertainty

about the rate of carbon uptake in carbon “sinks” —

the places carbon is stored after it leaves the atmosphere

(biomass, soils, oceans). This is a good

reminder that science deals as much with what isn’t

known as with what is known.

The increase of carbon dioxide in the atmosphere and

its potential effects on the Earth system led to the

signing of the Climate Change Convention in 1992 at

the UN Conference on the Environment and Development

(UNCED) in Rio de Janeiro, where 178 governments

were assembled for the first time to address

topics such as climate change, biodiversity loss and

economic development concerns. Work has continued

on the climate portion of the UNCED agenda through a

series of UN sponsored meetings to work toward a

carbon emission plan that developing and developed

countries can utilize to reduce carbon emissions.

Carbon Dioxide

55%

Methane

15%

Figure 3

The direct contributions of

greenhouse gases to global warming.

Nitrous Oxide

6%

Other CFCs

7%

CFCs 11 and 12

17%

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

19


A Global Change Primer (continued)

Methane

Methane, the second most significant greenhouse gas has as primary natural sources wetlands and termite metabolism.

Anthropogenic sources are coal mining, leaks in natural gas systems, rice paddies, enteric fermentation from the digestion

of grazing animals like cows, from animal wastes, landfills and biomass burning. Methane concentration in the atmosphere

has more than doubled from its pre-industrial levels and until recently was increasing at about 1% per year. Over

the last decade this rate has slowed and is now at about 0.6%. This is still a significant rate, especially when one

considers that each molecule of methane has many times the warming potential as a molecule of carbon dioxide (see

Global Warming Potential (GWP) below).

CFCs

Not all greenhouse gases are naturally occurring like carbon dioxide or methane. Some of the trace gases are artificially

manufactured and are new to this century. They include the chloroflurocarbons (CFCs), invented in the 1930s, and the

recently developed CFC-replacement family of hydrogenated chloroflurocarbons (HCFCs), hydrogenated fluorocarbons

(HFCs), and various compounds with bromine (halons). These trace gases often have long lifetimes in the atmosphere,

and on a per molecule basis, some are equivalent to thousands of CO 2

molecules in their greenhouse heat-rapping effect.

Coincidentally, CFCs and related chemicals are also responsible for the loss of ozone in the stratosphere due to the

release of chlorine and bromine when the compounds are transported by convection to the stratosphere and are exposed to

more intense ultraviolet light. Chlorine and bromine catalyze the destruction of ozone above natural rates. More about

CFCs and ozone later. Recent research has indicated that ozone depleting chemicals such as the CFCs, that have a direct

warming effect as greenhouse gases, also have an indirect cooling effect by removing ozone, which itself is a greenhouse

gas from the lower stratosphere. Because of this development, the net effect of some of the halocarbons as greenhouse

gases is unclear.

Tropospheric ozone

Tropospheric Ozone is a greenhouse gas of

increasing significance. This lower atmosphere

ozone is photochemically (chemical reaction

driven by sunlight) produced when nitrogen

oxides (NO x

) react with carbon monoxide (CO),

CH 4

, non-methane hydrocarbons (NMHCs), and

sunlight. Most of the pollutants which lead to

the formation of tropospheric ozone in cities

come from automobiles, power plants and other

human activities. In addition to its long-term

effects as a greenhouse gas, ozone is a major

component of “smog,” which causes significant

health problems for people in many cities,

notably acute respiratory disorders. Ozone at

Concentration of CO 2

(ppmv)

380

360

340

320

CO 2

Concentration Mauna Loa, Hawaii

Monthly

atmospheric CO 2

concentrations

300

1955 1965 1975 1985 1995

Year

Figure 4 Annual average carbon dioxide at

Mauna Loa Hawaii, 1958 – 1993.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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A Global Change Primer (continued)

ground level also has adverse affects on trees, and is thus implicated in the degradation and decline of forests. Tropospheric

ozone is thus the “bad ozone,” not to be confused with the “good ozone” in the stratosphere, which protects life

from excess ultraviolet radiation.

GWPs

In attempting to compare the effect of different greenhouse gases (there are dozens), the Intergovernmental Panel on

Climate Change developed the Global Warming Potential (GWP) for different gases. The GWP assigned to a gas is

basically a tool for policy discussions on the relative importance of different gases to the greenhouse effect.

By setting the greenhouse warming potential of CO 2

equal to 1, the effect of all other greenhouse gases can be calculated.

Gas

GWP†

CO 2

1

CH 4

11

N 2

O 270

CFC-11 3,400

CFC-12 7,100

HCFC-22 1,600

† time horizon of 100 years. From IPCC 1992.

Since different gases have different resident times in the

atmosphere, the GWP index is a time-integrated measure

of warming potential.

Modeling climate

It is important to know how the climate will change

globally, such as altered global average temperature and

precipitation, but for most of us we want to also know how

climate will change regionally, and even locally. Modeling

future climate at any scale is one of the challenges of

global change science. Information on radiatively

important gases, the role of clouds in warming or cooling

the Earth, and other variables are used to build

supercomputer models of the atmosphere. These models,

known as General Circulation Models (GCMs), are now

being developed to couple with models of the biosphere

and hydrosphere to gain insight into how Earth systems as

a whole interact.

Local Temperature Change (˚C)

2

0

-2

-4

-6

-8

-10

of CO 2

400

1990

level

300

280

260

240

220

200

180

Carbon Dioxide

300

280

260

240

220

200

180

0 40 80 120 160

Age (thousand years before present)

Figure 5

Carbon Dioxide Concentration (ppmv)

Methane

Entrapped methane, carbon dioxide, and

derived temperatures, Antarctic ice cores.

Adapted from IPCC 1990 Scientific Assessment.

700

600

500

Methane Concentration (ppmv)

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A Global Change Primer (continued)

A doubled CO 2

scenario

One experiment that is run on the GCMs is the climate response to a doubling of the CO 2

from pre-industrial levels. The

model experiment introduces a doubled CO 2

concentration into the model atmosphere and then the model is run until it

reaches equilibrium. Currently GCM’s give a range of global average temperature increase of between 1.5 and 4.5

degrees C for a doubled CO 2

scenario. Since the atmosphere is expected to have increased concentrations of greenhouse

gases in the next century equivalent to a doubling of CO 2

, the reliability of the GCMs is of critical importance in

determining a wise policy toward greenhouse gases, particularly carbon dioxide.

Is it getting hot or not?

Scientists agree about the physics of the greenhouse effect and they agree that since the industrial revolution, the

greenhouse gases have been increased by anthropogenic emissions. Now, has there been an observed rise in global

temperature? Yes. Over the past hundred years, a rise in global average temperature of about half a degree Celsius, or

close to one degree Fahrenheit has been recorded (fig. 6). Though it may not sound like much, one degree of temperature

is significant in global terms and might take nature thousands of years to bring about on its own (fig. 12)

The problem becomes even more serious when one considers that trends of greenhouse gas emissions are strongly

upward, due to population growth and increasing development around the world. Currently, the U.S. is the largest

Global Mean Temperature

Temperature Change ˚C

0.4

0.3

0.2

0.1

0.0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

1860

1870

1880

1890

1900

1910

1920

1930

1940

1950

1960

1970

1980

1990

Year

Figure 6

Deviations from a global temperature of 15°C for the period from 1854 to 1992. The average temperature of 15°C was

calculated from a reference period of 1950 to 1979. Data from P. D. Jones and T. M. L. Wigley, CDIAC 1991, 1993.

See page 119-120 for data set and full reference.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

22


A Global Change Primer (continued)

contributor to global greenhouse gas emissions, but as China, India, and other developing countries grow and industrialize,

their emissions are expected to surpass those of the U.S.

The phrase “global warming” refers to the predicted warming expected to result from the build-up of the above-mentioned

greenhouse gases. Scientists agree about the physics of how greenhouse gases respond to incoming solar radiation

and outgoing longwave radiation. What is difficult to know is whether the observed changes in global temperature are

caused by the increased concentration in greenhouse gases. Global average temperatures have been rising since the late

1970s, but could this be due to natural variability in the Earth’s system? It is hard to tell.

One place to look is temperature records of the past. By knowing the difference between the temperature at the peak of

an ice-age and in the middle of an interglacial period a sense of natural variability can be established on time scales of

tens of thousands of years. Its also important to know the rate of change for temperatures in the past. For example, is a

half a degree C change per thousand years, slow, fast or typical of past rates of change in the temperature record of past

climates (figurs 6 and 12)? As figure 6 reveals, the global average temperature has increased about 0.5 degrees C in

about the last 100 to 150 years. Is it now poised to go back down from the hot decade of the 1980’s or is it about to

exceed the natural variability and continue to increase?

So what’s a few degrees

In as little as a few decades, Earth’s climate could be as different from today’s climate as it was at the height of the Great

Ice Age, only warmer instead of colder. What would such a change mean for human life on Earth? One important

consequence of global warming is that sea levels will rise because water expands as it warms and due to increased

melting of mountain glaciers and polar ice. In fact, new satellite data confirms that sea level is rising consistent with

model predictions. The IPCC estimates that by the year 2030, sea level will likely have risen by 15 cm (about 6 inches),

and that by 2100 the rise will be 50 cm (about 20 inches). These estimates are based on a “business-as-usual” scenario,

i.e., on the assumption that humankind will continue to burn fossil fuels as its primary energy source, thus increasing the

atmospheric concentrations of greenhouse gases in the future much as it has done in the past. Low-lying parts of

Bangladesh, Florida and several Pacific islands would be significantly affected. About half the world’s people live in

coastal regions and this number is growing. Furthermore, some of the most fertile and densely populated regions are

found at the very lowest altitudes above present-day sea level.

Another ramification is likely to be widespread change in both natural and managed ecosystems. Change in physical

factors such as the maximum, minimum and average temperatures, the amount and seasonal timing of precipitation, soil

moisture, humidity, and wind have dramatic effects on living systems. Given enough time to respond to change, living

systems adapt as the fossil record reveals, but rapid change makes it far more difficult for successful adaptive strategies

to emerge.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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A Global Change Primer (continued)

Uncertainties

There is considerable uncertainty about how various elements of the climate system will respond to an enhanced greenhouse

effect. This uncertainty exists largely because as the climate warms, a lot of things begin to happen which we

cannot accurately predict; and these may lead to “feedback” effects which in turn influence the climate. As the climate

system changes, it generates processes that affect the original change. If one of these processes amplifies the change

(such as increasing warming) we call it a positive feedback. If it dampens the change, we call it a negative feedback.

The role of clouds is one these major uncertainties. We don’t know if cloudiness will increase or decrease as a result of

global warming, or how much the altered clouds will reflect sunlight away or retain heat in the atmosphere. We don’t

know if clouds will act as a stabilizer or amplifier of climate change. There is also uncertainty about how ocean circulation

may change in response to warming and if ocean circulation changed, how it would affect climate.

Given that there is uncertainty about the Earth system response to global change factors like an enhanced greenhouse

effect, when is action merited? If we wait for greater certainty, it may well be too late to act effectively to slow the

process and adapt to it. On the other hand, if we act with poor information, our actions could be damaging or wasteful.

One approach is to take action that makes sense for other reasons. Examples include increasing energy efficiency and

accelerating the transition from fossil fuels like coal to renewable or more benign sources. Making changes such as

these will also help with other problems such as acid rain, and urban smog.

The protective ozone

The ozone layer is a blanket of ozone (O 3

) molecules in the stratosphere that protects Earth’s inhabitants from excess

ultraviolet radiation from the sun. Ozone is continually being created, destroyed and transported around the globe by

winds. The amounts vary both by latitude and season, with the lowest concentrations occurring near the equator and

highest amounts near the poles. This means that living things in the tropics are least protected from solar ultraviolet

radiation and therefore must have developed the strongest defense mechanisms against it.

The depletion of the ozone layer by human-made chemicals is a global change issue of enormous importance, and unlike

climate change, there is a high degree of certainty about cause and effect, and what we can do about it. Measurements

reveal losses of up to about three quarters of the ozone over the South Pole in Spring time (the ozone hole) as well as

significantly reduced levels of ozone globally. There is nothing hypothetical about this problem - it has been happening

for decades and human activity is the cause. Moreover, ozone depletion raises serious health concerns for humans and

other species.

The Culprits - CFCs and Halons

The major culprit is a family of gases called halocarbons, most notably CFCs and halons. Entirely artificial, chlorofluorocarbons

(CFCs) were invented about 60 years ago as coolants for air conditioning and refrigeration. They have also

been used as propellants for aerosols, blowing agents for plastic foams, and solvents for electronics. Halons are used

primarily in fire extinguishers. In the 1970s, scientists began to discover a very serious down side to these two groups of

24

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A Global Change Primer (continued)

wonder chemicals. The chlorine from CFCs, and the bromine from halons, destroy

stratospheric ozone molecules, and each atom of these elements can destroy

thousands of ozone molecules.

The Ozone Hole

In the 1970s, two scientists predicted that CFCs would cause a global decline in

stratospheric ozone. Years later satellite sensors recorded a drop in ozone over

Antarctica, and even flagged the lowest values, but the ozone levels were so low,

they were outside the range the computers had been programmed to accept as valid

data and so the early warning was missed. Looking back at the data revealed that in

1984, the unsuspected ozone hole was already larger than the continental U.S. By

1987, the average ozone concentration over the South Pole was down 50%; during

springtime it was down 70%, and in some spots, had essentially disappeared

altogether. By 1992, the ozone hole had grown in area to nearly three times the size

of the continental U.S. Though scientists had predicted the global decline in

stratospheric ozone, no one had anticipated that ozone loss would appear so

dramatically and suddenly in the form of a “hole” in the ozone layer over Antarctica.

1979

1980

1981

1982

< 390 DU

< 240 DU

Concentration

< 240 DU

< 390 DU

If chlorine and bromine from CFCs and halons released from populated areas cause

ozone destruction, then why is the ozone hole at the South Pole? The CFCs and

halon sources are primarily from the mid-latitudes and after their release are

transported by convection to the upper atmosphere and eventually the stratosphere.

There are a couple of unique features that make the stratosphere over the poles

particularly the South Pole more susceptible: First, Antarctica and the air above it

is extremely cold and this leads to the formation of Polar Stratospheric Clouds

(PSCs). Tiny ice crystals in PSCs provide chemically-active sites where the

chlorine and bromine can catalyze the breakup of the ozone. The other feature is

the polar vortex, a spiral of winds that swirls around the South Pole, isolating the

Antarctic stratosphere during the winter and early Spring so the ozone destruction

process goes on without Antarctic ozone being replenished by ozone rich air from

lower latitudes.

1983

1984

1985 1985

Global Ozone Depletion

But ozone losses are not confined to the South Pole. In 1988, over 100 international

experts reported that the ozone layer around the entire globe was eroding much

faster than anticipated. Between 1969 and 1986, the average global concentration

of ozone in the stratosphere had fallen by approximately 2%. By 1991, losses of 6

to 8% per decade had been measured at high latitudes (nearer to the poles) and

Figure 7

These pictures show the

increase in size of the Antarctic

ozone hole during successive

winters. October monthly

average TOMS total O 3

. The

crosses indicate South Pole.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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A Global Change Primer (continued)

losses of 3 to 5% per decade appeared at mid-latitudes (closer to the equator). Global average ozone in 1992 was 2 to 3%

lower than the lowest level previously observed, and 1993 measurements broke even those records.

Ozone and life

What does declining ozone mean for human beings or other forms of life? Less stratospheric ozone means more ultraviolet-B

(UV-B) radiation and that means more sunburns, skin cancer, cataracts, and immune system deficiencies, other

factors being equal. It is estimated that each 1% decline in ozone allows about 2% more UV radiation to reach Earth,

and is thus projected to result in 4-6% more cases of the most common types of skin cancer. In 1991, the US Environmental

Protection Agency estimated that over the next 50 years, about 12 million Americans (equal to the entire population

of Florida) will develop skin cancer, and more than 200,000 of them will die from the disease (a 50% increase over

the current death rate from skin cancer). Also, ozone depletion has continued to worsen, so if the EPA estimate is valid,

the numbers would now be even higher. Having light skin coloring, living near the equator, and living at high altitude

increases the risk of exposure to UV-B.

New research strengthens the link between ozone depletion and increased ultraviolet-B (UV-B) radiation at Earth’s

surface. UV-B is radiation from a portion of the ultraviolet spectrum (from 290 to 320 nanometers; a nanometer is a

billionth of a meter) to which many living organisms appear to be especially sensitive. Researchers in Toronto, Canada

measured UV-B levels at various wavelengths and found that at 300 nanometers (a wavelength at which ozone absorbs

UV-B), the intensity of the radiation reaching Earth’s surface at the test site shot up, with summertime levels increasing

by 7% per year and wintertime

intensities increasing by 35% per

year from 1989 to 1993. The

summertime increases, though

smaller in percentage, may prove

even more damaging to humans

and other living things as they are

occurring at a time of year when

UV-B is already at its highest

levels in Canada and people are

outdoors for longer periods of

time.

The Montreal Protocol

Beginning in the 1980’s representatives

from industry, the science

community, governments got

together under the auspices of the

United Nations to address the

Figure 8

Chlorine loading of the stratosphere as modified by international agreements.

Adapted from NASA Goddard Space Flight Center, WAL-144, January 1994.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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A Global Change Primer (continued)

ozone issue. This dialogue led to the Montreal Protocol which set limits on some of the ozone damaging chemicals.

Subsequent international meetings in this process prescribed more stringent restrictions and phaseouts of damaging

chemicals (figure 8).

Addressing the Problem The Montreal Protocol

Since the 1985 revelation of the ozone hole, global stratospheric ozone levels have continued to decline, and the Antarctic

ozone hole has grown considerably larger. The magnitude of the problem is so large that even if we stop producing

the offending compounds immediately, scientists estimate it will take several generations for concentrations of chlorine

monoxide (the key molecule in ozone destruction) in the stratosphere to return to pre-ozone-hole levels. In spite of such

distressing news, there is cause for guarded optimism. An international effort is underway which intends to help slow

and eventually stop further ozone depletion and it appears to be having some effect. How did this unprecedented effort

begin?

By the mid-1970s, many experts had grown convinced that chlorofluorocarbons (CFCs) and other similar compounds

posed a serious threat to the ozone layer. In the U.S. - the world’s largest producer and user of CFCs - the public called

for the government to place limitations on these chemicals. Boycotts against items that used CFCs were launched, and

some companies eliminated the compounds from their products. The U.S. government responded in 1979 by banning the

sale of aerosol cans containing CFCs. Because spray cans represented the largest use of these chemicals, the ban led to

an abrupt leveling off of CFC production.

But the U.S. ban on CFC propellants in spray cans caused only a temporary pause in the growing demand for the

compounds. Worldwide use continued and by 1985, the production rate was growing by 3% a year. (A 3% growth rate

means that production would double in about 23 years.) This increase brought the world’s attention back to the threat of

ozone depletion, prompting the 1985 signing of the Vienna Convention, an agreement to draw up a plan for worldwide

action on this issue. Then, in May of 1985, British researchers reported the discovery of the ozone hole over Antarctica.

This news spurred the nations of the world to action.

In 1987, diplomats from 24 nations, representing most of the industrialized world, forged a remarkable treaty, agreeing to

set sharp limits on the use of CFCs and halons. In addition to such unprecedented international cooperation, the treaty

marked a unique example of scientists and industry working with governments to seek a global solution to an environmental

challenge. The Montreal Protocol on Substances that Deplete the Ozone Layer declared that by 1989, production

of halocarbons (CFCs and halons) would be frozen at 1986 levels and then cut in half over the next decade. The framers

of the Protocol also realized that their agreement might not suffice if future research revealed an even greater threat. So

they included a provision calling for negotiators to reconvene periodically to examine new evidence that might necessitate

deeper cuts.

Such evidence did indeed come to light, and several revisions have since been made. The 1990 London amendments and

the 1992 Copenhagen amendments sped up the halocarbon phase out and controlled several other chemicals that were not

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

Figure 8

27


A Global Change Primer (continued)

in the original agreement: methyl chloroform, carbon tetrachloride, methyl bromide, and HCFCs

(hydrochlorofluorocarbons, replacements for CFCs which are less ozone-depleting than CFCs but not totally ozone-safe;

HCFCs are also “greenhouse gases,” contributing to global warming). The revised agreement now calls for the phase-out

of CFCs to be complete by 1996. The treaty also attempts to make the phase-outs fair to developing countries, which

cannot easily afford to make the transition to higher-priced substitutes that will replace the banned compounds. The

revised agreement sets up a fund - paid for by developed nations - to assist developing countries in making the switch.

Good News and Bad News About the Treaty

The good news is that the treaty is already beginning to have an effect. Significant decreases in the growth rates of CFC-

11 and CFC-12, which together account for half the total chlorine monoxide in the stratosphere, were reported in August

1993. If the growth rates of these two CFCs continue to slow in line with predicted changes in industrial emissions,

emissions should peak before the turn of the century and then begin to decline - sooner than predicted.

The bad news is that even if the treaty process continues to work, there will be elevated levels of chlorine and bromine

compounds in the stratosphere able to continue catalyzing the destruction of ozone for generations to come, perhaps well

into the 22nd century. So even though the response to the ozone problem is on track toward a solution, the effects of this

human caused change to an important part of the Earth system will linger with unclear consequences to life on Earth.

Biodiversity loss

Of all the human-caused global change challenges we face, one of the most dramatic and irreversible is the increasing

extinction of the world’s species. As with other issues in global change, extinction is a natural part of a changing Earth.

However, the rate at which species are now facing extinction is cause for concern. Due to human activity, the current

rate of extinction is far greater than the estimated natural rate of species extinction that has prevailed for millions of

years. And unlike air or water pollution, or even deterioration of the ozone layer, loss of biodiversity is irreversible.

Once a species is gone, you can’t get it back, because it took millions of years to become what it was. It is currently

believed that we are losing perhaps as many as 10 to 20 species per day, up to 7,000 each year.

Biodiversity has to do with the variety of living things in an ecosystem. No one knows how many species exist on Earth,

though current estimates range from 5 to 100 million. Only about one and a half million species have been catalogued to

date. The large numbers of species now being forced to extinction by human activity has been likened to burning down

the world’s greatest library before anyone had even catalogued, let alone read the books.

Habitat destruction

What do humans do to cause this great loss? People have cleared forests and other critical habitat to expand farming,

ranching, mining, fishing, and other activities. When humans cut down forests to create grazing land for cattle, for

example, species that depended on those sections of forests are eliminated or forced into smaller and smaller areas and

may finally succumb to extinction. Take for example Western Ecuador, which once contained an estimated 8,000 to

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A Global Change Primer (continued)

10,000 plant species, about half of them endemic to the region. Each plant species supports between 10 and 30 animal

species. Since 1960, nearly all the western Ecuadorian forests have been cleared for banana plantations, oil wells, and

human settlements. The number of species lost in this area in just 25 years is estimated at 50,000.

Introduced Species

After habitat loss, the next most important factor in loss of biodiversity is biological invasion by non-indigenous organisms.

Biological invasion occurs by accident and by design. The intentional introduction of a species for a particular

purpose, such as a new agricultural crop, weed control, pest control, or erosion stabilization are invasions of the first type.

Invasion by accident occurs where plants and animals are introduced without human design, such as the introduction of

the Zebra mussel into the Great Lakes from the ballast water of ships from foreign ports. The mussels attach to and clog

freshwater intake pipes that supply cities along the lakes. Billions of dollars are spent each year in attempting to deal

with the unwanted effects of biological invasion, but how is it a threat to biodiversity and how is it a global change?

Much of the new disturbance of species by invaders is the byproduct of ever-increasing numbers and movement of

human beings around the globe. Unique flora and fauna of islands and island continents like Australia is due to the long

term biological isolation created by the physical separation of the continents beginning hundreds of millions of years ago.

As continents drifted apart, the physical separation enabled separated species to evolve on different continents for

millions of years in isolation. Once physically and biologically separated, the process of evolution began to fill similar

habitats in unique ways. The marsupials are an example of this process, very different from mammals in form, less so in

their ecosystem function.

Human activity has created artificial “bridges” between the continents and geographically isolated regions of the world

through trade, tourism, and agricultural development. Human activity is blurring or homogenizing the flora and fauna of

distinct geographic areas, but wouldn’t new species in an area increase biodiversity?

Some invaders become dominant in their new environment and crowd out native species. In some unique situations, they

are so successful at displacing the natives become extinct. As more of the land surface becomes altered by human

activity, the displaced species has no other place to go with suitable conditions for survival.

The appreciation that global changes such as climate change, stratospheric ozone loss, tropospheric pollution, and land

use change, affect biodiversity has increased over the last decade. The recognition of the value of biodiversity has led to

a UN process similar to the Climate Convention, but with the issues of biodiversity as its focus.

The change in human population

Human activity on the planet drives global change. It took perhaps two million years to get from the beginning of the

human era on Earth to a population of two billion. And then, in only 30 years, another billion people were added.

Human population doubled, from 2.5 to 5 billion, in just 37 years, and it is now increasing by about 90 million people a

year. Each month, the world adds the equivalent of the population of Switzerland. About 94% of this growth is occur-

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A Global Change Primer (continued)

ring in the developing countries, home to 78% of the world’s population, where local life-support systems are often

deteriorating as human demands exceed the capacity of available resources.

Earth’s human population is expected to double again, topping ten billion in the next 50 years or so. Each human has

energy and resource requirements that affect the Earth system. When these effects are taken in total the result is global

change. Finding a sustainable path is a challenge today and a necessity in the coming century. Better understanding of

population-environment dynamics is a critical area of global change research and one that unites the social and natural

sciences.

Non-Human Influences

Were it not enough that human beings are causing significant change in Earth’s systems, consider the fact that there are a

multitude of non-human disturbances occurring as well. Variations in solar radiation, volcanic eruptions, earthquakes,

meteor impacts, and other such planetary traumas can certainly throw a wrench into our “planetary management” efforts.

As discussed, Mt. Pinatubo is a recent example that reminds us of the importance of change to the Earth system from

natural causes. Though such events are completely out of our control, we must respond to their impacts nonetheless. The

better we understand these phenomena, the better equipped we will be to prepare for and manage their effects.

The Challenge Ahead

As evidenced by major extinction events and the fossil record, extinction and the evolution of species is a process that

marches forward with or without our influence. Fortunately many of the global changes discussed here are becoming

better understood. With this knowledge comes the ability to make wiser choices and a better view of where we are

heading. It seems especially important at this juncture for young people to learn about Earth systems and global change

as a necessary step in building the capacity to care for generations to come.

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Remote Sensing & Ground Truth Primer

An Introduction to Remote Sensing and Ground Truth

It is said that the human eye provides us with about 90% of the information we receive about our environment. As well

as giving the most varied information, visual appearance is the only source of information at great distance, without the

aid of complex instruments. Since we are so visually oriented, people have long been striving to develop technological

means of continually expanding our ability to see.

Remote sensing is the process of obtaining information from a distance, especially from aircraft and satellites. Modern

remote sensing technology has greatly expanded our ability to see and understand the Earth and its systems and to

observe spatial patterns and change over time. Remote sensing has become a critical tool in activities ranging from the

verification of arms control treaties to the provision of emergency aid to disaster-stricken regions. Through remote

sensing we learn about problems such as droughts, famines, and floods; we obtain information about agricultural

practices, weather conditions, transportation systems, river flows, and terrain changes. We use remote sensing to locate

Earth’s natural resources and can then use that information in their management.

Light and the Electromagnetic Spectrum

Because most of the data we receive from remote sensing comes to us in image form, the light which produces images is

central to the process. Light gives us two different kinds of information about objects. Size, shape and texture are

revealed by the way the object is illuminated and shadowed in relationship to the light source. The second kind of

information comes mainly from the way light is absorbed and reflected by the object; this information shows up as the

object’s brightness and color.

Light is a form of electromagnetic radiation (figure 9). Only a small part of the electromagnetic spectrum is visible light.

Wavelengths just shorter than visible are ultraviolet (UV) and wavelengths just longer than visible are infrared.

O.4µm 0.5µm 0.6µm 0.7µm

1pm 10pm 100pm 1nm 10nm 100nm 1µm 10µm 100µm 1mm 10mm 100mm 1m 10m 100m 1km

WAVELENGTH (meters)

GAMMA RAY

X-RAY

ULTRA-VIOLET

VISIBLE

uhf vhf hf mf lf

RADAR

RADIO BANDS

MICROWAVE

NEAR MID FAR

INFRARED

Figure 9

A diagram of the electromagnetic spectrum. It is important to note the location of

visible light and that it occupies only a small portion of the electromagnetic spectrum.

AUDIO

FREQUENCY (Hz)

10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 10 2 1

AC

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Remote Sensing & Ground Truth Primer (continued)

Sensors

In the process of remote sensing, information about our environment is conveyed by electromagnetic energy and received

and recorded by sensors. Most modern technological sensors have counterparts that occur in nature. For example, the

photographic camera and the human eye both sense visible light; the microphone and the ear pick up sound waves; smoke

alarms and noses both sense molecular dispersions we call odors. The sensors used in remote sensing are primarily

sensitive to UV, visible, infrared, and microwave wavelengths; they sense and record data in these spectral bands. These

data are then generally converted to image form for print or computer viewing and enhancement. Radar senses in the

microwave region of the spectrum; the Landsat thematic mapper sensor senses in the visible and near to mid infrared.

Platforms

The physical platforms that carry sensors affect their capabilities and provide their perspectives. Platforms for remote

sensing can be on land or in water, air or space. Aircraft platforms are typically flown at altitudes between 3,000 and

21,000 meters (figure 10). The data they deliver are either digital or photographic. The information we receive from

space is generally digital and comes from NOAA weather satellites like GOES, earth resources satellites like Landsat and

SPOT, and from manned missions such as the Space Shuttle. In the near future, information will also come from the

SeaStar ocean color satellite, as well as the Earth Observing System (EOS) satellites, which will make a wide range of

environmental measurements.

Landsat

700 km

Landsat

700 km

High Altitude Aircraft

High

up

Altitude

to 12 km

Aircraft

up to 20 km

Low Altitude Aircraft Aircraft

up to 10 6 km km

185 km

18 km

9 km

Figure 10: Altitudes of three commonly used remote sensing platforms and the approximate width of their images.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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Remote Sensing & Ground Truth Primer (continued)

Altitude, Scale, and Resolution

Several common characteristics of all images, regardless of the sensor from which they come, help us in understanding

the information they can provide about land cover. Scale, the ratio between the size of the image of an object and the size

of the actual object, is a primary concern. Spatial resolution of an image is closely related to scale. Spatial resolution

refers to the smallest object that can be detected in an image, and is stated as a linear dimension (e.g., the AVHRR sensor

has 1 kilometer resolution, whereas the SPOT panchromatic sensor has 10 meter resolution). Spectral resolution

indicates the portion or band of the electromagnetic spectrum recorded by a sensor. Temporal resolution is the time

interval between measurements of the same location on Earth. For example, Landsat views the same location every 16

days, whereas NOAA satellites view the same location every day, or even twice a day.

The spatial resolution of satellite images is determined by the size of the picture elements or pixels (figure 12, page 52).

Pixels are like mosaic tiles or square puzzle pieces that are arranged in rows and columns to make up the whole image.

All the information within each pixel is averaged together into a single value so that objects or features smaller than the

size of the pixel are not distinguishable.

Processing Data

Data processing is the intermediate step between collecting remotely sensed data and using the information derived from

it. Most data processing involves image enhancement and analysis. Images can be analog (photographic) or digital

(electronic) - that is, continuous tone on photographic film, or digitized pixels of information stored on electronic media

such as magnetic tape.

Analog and Digital

An analog image refers to an image in which variation in the object being sensed is represented by a continuous variation

in image tone, such as in a photograph. Photographs capture large amounts of data all at once; however, they cannot be

directly manipulated by a computer unless they are first converted to a digital format.

A digital image refers to an image made up of pixels where the average brightness or tone within each pixel is represented

by a single number. The numbers are often simple counts in which the count indicates the brightness level of the

pixel. When data are captured in discrete wavelength bands, each spectral band is a separate digital image (this kind of

data is called multispectral). Electronic digital computer processing is generally more flexible and more quantitative than

photographic processing.

Displaying the Information

Remotely sensed images are usually displayed as color prints or on computer screens. Three different spectral bands can

be displayed simultaneously using three colors: red, green, and blue. When red, green and blue spectral bands are

displayed using the same three colors, the result is a ‘true color’ image. However, when these three colors are used to

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Remote Sensing & Ground Truth Primer (continued)

display different spectral bands, the image is called a ‘false color’ image. In color infrared photography, the color red is

traditionally assigned to the near infrared band, which results in healthy vegetation showing up as vibrant red, because it

radiates strongly in the infrared region of the spectrum. At first, one may be disoriented by the “false color” of color

infrared images. There is a “standard” color key used in color infrared imagery, but a scientist studying a specific feature

with a particular reflectance or emittance characteristic might choose to highlight these features by assigning different

color codes.

Geographic Information Systems

Geographic Information Systems (GIS) use computers to combine remote sensing data with other information (e.g.,

topographic, political, cultural, economic, ground truth). In essence, a GIS is a way of managing Earth science data to

bring out geographical interrelationships. Such systems provide powerful ways to use and compare remote sensing data.

A satellite image of a country’s vegetation can receive overlays of roads, district or county boundaries, population

statistics, etc. In essence, a GIS is a database management system specifically designed for simultaneous processing of

spatial data with many capabilities similar to automated map making.

Ground Truth

Ground truth refers to field observations and measurements which provide the link between remotely sensed data and the

environmental information that is desired. Satellite data can often be ambiguous, since the information is based on

radiation measurements with limited spatial and spectral resolution. For example, forests can usually be distinguished

from fields, and sometimes the type of trees present (deciduous vs. conifers) can be inferred. Scientists may then visit a

forest to verify that it is composed of pine trees. The field data gathered is called “ground truth.” Such “ground truth”

information may be used calibrate the remote sensing data for local conditions, and to interpret and analyze the data. It

may also be used to validate the results of the interpretation and analysis process. Ground truth observations by students

can be used to analyze aerial photographs and satellite images of their own location.

Teaching Remote Sensing and Ground Truth

Remotely sensed images may be used very successfully as educational tools with students of all ages. It is sometimes

useful to begin with images closest to your neighborhood and progress to images obtained from greater distances. For

example, start with hand-held photos and then move to low-altitude aerial photos, to high-altitude aerial photos, and then

to satellite images. The false color may initially be confusing, but this can be quickly remedied by explaining that it is

similar to assigning a color code to a map. When remotely sensed images are compared to maps, the effects of scale

should be considered to avoid confusion about an object appearing larger on one than the other.

Remote sensing and ground truthing are activities that make use of knowledge and skills which students acquire from

many traditional school subjects. Their improved ability to “see” and understand their world can bring them closer to

experiencing the interdependence of all life and the complex systems of planet Earth.

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Activities

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Activities by Grade Level

Kindergarten through grade 3

Learning to Look, Looking to See* / 39

Just Right: The Goldilocks Effect / 43

Where Are You From A Bird’s Eye View? / 45

Sandboxes and Satellites / 47

Grade 4 through grade 6

Learning to Look, Looking to See / 39

Just Right: The Goldilocks Effect / 43

Where Are You From A Bird’s Eye View? / 45

Sandboxes and Satellites / 47

Digital Faces / 49

Zooming In / 53

Ground Truthing Your Image / 67

Investigating the Invisible / 71

Dust Busters / 85

Back to the Future / 89

Grade 7 through grade 12

Learning to Look, Looking to See / 39

Just Right: The Goldilocks Effect / 43

Where Are You From A Bird’s Eye View? / 45

Sandboxes and Satellites / 47

Digital Faces / 49

Zooming In / 53

Ground Truthing Your Image / 67

Investigating the Invisible / 71

How When Affects What (Parts I, II and III) / 73

Dust Busters / 85

Dead Right, Dead Wrong / 87

Back to the Future / 89

Map Your Watershed / 91

Landcover Mapping / 93

A Changing Watershed / 97

Your Watershed’s Story / 101

Make a Watershed Model / 105

River Walk / 109

Regulatory Agencies on the River / 113

* From Project WILD, adapted with permission

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Learning to Look, Looking to See —

Silent Walk

From Project WILD: adapted with permission. © 1983, 1985 Western Regional Environmental Education Council.

Objectives

Students will be able to: 1) describe differences seen in

an environment as the result of casual and detailed

observations; and 2) give reasons for the importance of

looking closely at any environment.

Method

Students list what they remember seeing in a familiar

environment, check their accuracy, and discuss the

results. Then they apply their experiences and new skills

to an unfamiliar outdoor setting. It is very useful to

repeat this activity several times, because students like to

try to “get better” at it. Repeating it at different seasons

produces interesting results which can be related to the

seasonal differences detected by satellites.

Background

Looking and seeing are two entirely different processes

depending on who we are, what we are concerned about,

where we are located, and why we are looking. We look

at our classrooms every school day, but if questioned

about simple details, we often discover that we are totally

unaware of certain objects, colors, sounds, and textures.

As we walk through our neighborhoods, we probably

notice only those things which are necessary to aid us in

getting to our destination. We may not see a soaring bird

even though we may be looking at the sky. We may not

notice a community of ants, even though we are looking

at the sidewalk. During a walk in the woods, we may

leave the trail to see a tree better — and then not see the

wildflower we trample, even though we are looking at

the forest floor as we walk to the tree.

Each of us, however, can train ourselves to see or sense

more. This takes at least three elements: 1) to learn to be

a careful observer, even if we do not have sight through

our eyes; 2) to be aware of our surroundings; and 3) to

Age

Grades K-12

Subjects

Language Arts, Science, Social Studies, Art

Duration

45+ minutes

Skills

comparing, classifying, describing, discussion,

inferring, listing, observation, predicting

Key Vocabulary

appreciate, see, sense, observe

recognize any part of our environment as being part of a

larger whole. As we enter a forest community, for

example, we become part of that community in much the

same way as we are part of our school or neighborhood

communities. Thus, we are members of every community

we enter. As a result, we have an opportunity and an

obligation to see our neighbors and to be responsible

members of each of these communities.

The major purpose of this activity is for students to be

given an opportunity to enhance their powers of “seeing.”

Materials

note pads, lapboards/clipboards

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Learning to Look, Looking to See (continued)

Procedure

1. Have your students pair off and sit back to back with

their partners. Without looking, each student lists the

color of their partner’s eyes, hair color, etc., and a

description of what they are wearing. After a few

minutes, have them turn around and check to see if

they were right.

2. Now practice seeing things. Cover a desk, bulletin

board, or table with a large sheet before students

come to class. Ask your students to list all the things

they thought they saw there before the area was

covered. When their lists are completed, ask them to

turn over their papers. Remove the sheet. On the

backside of their first lists, have your students make a

new list of what they see. What kinds of things did

they remember? What kinds of things were most

often missed? Let them come up with reasons why

they think this happened.

3. Take your students outdoors and have each pick a

spot near a tree, fence, brook, field, etc. Each student

should find a spot alone, at least 50 feet from the

closest human neighbor. Allow 15 minutes for this

solo, or approximately five minutes for younger

students. Your students should sense or “look” in

the broad sense of the word — seeing, touching,

listening, and smelling.

They should record everything they “see.” Fifteen

minutes will provide time for an initial spurt of

observations, a plateau, and then another spurt as they

begin to realize how much they missed the first time

around. (Younger children need only record in their

minds; no need to write.)

Note: Our role as teachers is a difficult one in that we

are most effective when we teach our students how to

look and see, without telling them what to see.

4. Bring your students together for a discussion of the

process they went through, as well as their list of

sightings. Did they focus on any one area for a long

time? Did they continue to shift their gaze? How did

they focus their hearing and smelling? Cupping hands

around their ears to simulate animal hearing has a

dramatic effect on the ability to hear. Blindfolding

seems to cause a compensation toward better hearing

as well. Moistening the undersurface of the nose and

the entire upper lip area increases smelling ability.

Repeat the exercise using these suggestions. How are

the results different?

5. Discuss the two statements: “Can’t see the forest for

the trees” and “Can’t see the trees for the forest.”

6. Talk with your students about the joy and importance

of seeing as fully as we can — as a way of appreciating,

respecting, and learning more about the world in

which we live. Older students: Discuss the importance

of careful observation of our environments

beginning with the basis for our fundamental life

support systems — air, water, land, plants, and

animals.

7. Optional, with older students: Talk about the process

of sensory attenuation as being a life-long process for

each of us. We are always learning, and can learn

even more. Sensing more in our surroundings can

help us detect changes in our environment, cause us to

become curious and ask questions, and help us to

become better, more aware and informed decisionmakers.

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Learning to Look, Looking to See (continued)

Extensions

1. Blur your eyes. What patterns and shapes do you see?

2. What else did you see? Any living things? What

were they? Were they plant or animal?

3. Categorize what was observed as living/non-living —

and/or as animal, plant, mineral.

4. Play the game “Animal, Vegetable, Mineral” or

“What Am I?”

5. Repeat with different groups focusing on the different

senses (sight, sound, smell, touch, etc.)

Discussion

Relating this activity to Remote Sensing and Ground

Truthing.

It is difficult, often impossible, to see everything at once:

to watch for birds in the sky while paying attention to

ants, trees and wildflowers on the ground. We must often

decide what we want to see before we can look for and

find it. Thus, the question we ask determines what we

will find.

Before scientists can “sense” the Earth, they must decide

what it is they want to “see”. The proper instruments and

sensors must be developed and sent into space or put on

an aircraft and flown over the area of interest. By

carefully selecting the best instruments for recording the

most relevant data, scientists can acquire the exact

information they need.

When we “ground truth” an area, we are able to “see”

much of what may be missing in a remotely sensed

image:

• An aerial image may indicate the presence of a

forest; on the ground, we can determine the species

of trees.

• A satellite may detect water; on the ground, we can

determine whether it is a breeding site for diseasecarrying

mosquitoes.

• An infrared image may indicate uneven coloration

of a crop, such as corn; on the ground, we can

determine whether the crop is diseased or unevenly

watered.

Armed with this information, we can make hypotheses

about other, similar areas on the same or other images.

For example:

• We can estimate the extent of oak forests.

• We can predict breeding sites of malaria mosquitoes.

• We can warn farmers of a regional outbreak of a

corn pest.

Learning to Look, and Looking to See are essential

elements of ground truthing.

Just as scientists develop better sensors to put on a

satellite, we can train ourselves to become better

observers, by paying better attention to our senses. We

can become aware of a bird hidden by the leaves of a tree

just by opening our ears to listen for its call. We can

“see” not just the bird, but the species of tree it is in. We

may notice a wildflower first by its perfume, or a change

in the weather by a cool breeze or the sudden warmth of

the Sun.

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Just Right: The Goldilocks Effect

Objectives

Students will be able to: 1) explain perspective, range

and resolution; 2) explain how the optimal viewing zone

varies with what it is they want to know—how the

“Goldilocks Principle” applies: they can be too hot (too

close), too cold (too far), or just right for any given

investigation.

Method

Students view a large object such as a poster, store front,

or even a brick wall from various distances and observe

the difference in the information they can get from each

perspective. The experiment can be repeated with

arrangements of other common objects.

Background

The Goldilocks Effect is a term used by astronomers

when comparing the distances from the Sun and the

climates of Venus (too hot), Mars (too cold) and Earth

(just right). Similarly, when aerial and satellite photographs

are used to gather information about the Earth, the

distance, range, and resolution of the pictures to be taken

are determined by considering what data is required for

the given investigation. For example, if you want to map

forest cover, you do not need nor want to see each tree,

and vice versa. In the activity, Learning to Look,

Looking to See, students learned to turn on their sensors.

In the “Goldilocks” experiment, students will grasp the

concept that being closer is not necessarily better or more

informative — the optimal point of observation, or

perspective, depends upon what it is that you want to find

out.

Age

Grades K-12

Subjects

Science, Math, Language Arts,

Duration

30-60 minutes

Skills

analysis, observation, prediction

Key Vocabulary

data, distance, perception, perspective, range, remote

sensing, resolution

Materials

A large sign or poster, metric ruler or measuring tape,

chalk, magnifying glass, note pads to record discoveries.

For younger students, cookies or their names on tags as

mentioned under procedure is a good variation.

Procedure

1. Set up a large poster, photograph or sign on an outside

wall of the school at eye level, in a location that allows

you to view the poster from far away (a gymnasium or

a long hallway are a good indoor alternatives). Bring

the class into view of the poster from so far away that

they cannot tell what it is.

2. Have your students slowly approach the poster in

small groups or one at a time. Have them approach in

stages of an appropriate distance (maybe 10 meters or

paces each time) and at each stage have them write

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Just Right: The Goldilocks Effect (continued)

down what they see and what they think is on the

poster. Have them continue until they can identify it.

At that point, they should stop and mark the ground

with chalk. They should then continue approaching

the poster until they are so close they can no longer

tell what it is. At this point, they mark the floor

again. Finally, have them move right up to the poster

and examine some detail of it with the magnifying

glass and record what they see.

3. Students then measure the two distances from the

poster. These distances define the range or “window”

within which their “remote sensors” (eyes) are

capable of gathering the most useful information.

That window might be called the “Goldilocks

Window” — not too hot, not too cold, but just right

— for gathering information about the poster.

Extension

1. Give a slide show or show a video on the possibilities

and limitations of remote sensing and the different

“windows”. A slide set and a video on remote sensing

are available through the Aspen Global Change

Institute.

2. Watch the video “Powers of Ten” and discuss the

differences in perspective each power of ten reveals.

(Available through most libraries, or order the VHS

cassette “The Films of Charles & Roy Eames, Volume

One, Powers of Ten” from Pyramid Film and Video,

Box 1048, Santa Monica, CA 90406 / 800-421-2304)

Discussion

1. Your students should discuss what kinds of information

they observed from each of the various distances.

They should try to frame questions that can be

answered only from close up, but not from far away,

vice-versa, and some questions that can be answered

only from a medium distance.

2. You can then explain that when people want to know

something about the Earth, they sometimes take

pictures of it from airplanes and spaceships so they

can get a perspective which is different from the one

they have when looking at it from the ground. This is

just like how your students got different perspectives

on the poster from varying distances. Scientists

gathering data by remote sensing do the same kind of

exercise that your students just did. They figure out

just how close or far away the camera needs to be to

give them the information they want. Using analogies

such as this, young students can begin to understand

the concept of remote sensing and how it is used.

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Where Are You From

A Bird’s Eye View?

Objectives

Students will be able to: 1) interpret an aerial photograph

of their town and locate their school, neighborhood, and

travel routes; 2) discuss and explain what kinds of

information they can obtain from aerial photos.

Method

Students will first try to imagine what their school and

neighborhood look like from “A Bird’s Eye View” and

draw a detailed picture. They will follow this with a

study of an aerial photo of their town. They will

compare their pictures with the aerial image and answer

questions based on the information it supplies.

Background

We often have an idea of the area in which we live, but

we rarely have the opportunity to test our “minds eye

view” against accurate information. Even good maps are

at best a stylized representation of our neighborhoods.

Large scale aerial photographs of familiar surroundings

help young students understand the concept of remote

sensing. This kind of photography is remote, but not too

remote, and being able to find places they see everyday

makes the activity relevant and exciting for your

students. This exercise should also help develop your

students’ geographical literacy.

It may be helpful to refer back to the Primer on Remote

Sensing, at the front of this book, before beginning this

activity. At first, the color infrared images may confuse

your students, but with a small amount of coaching, and

pointing out some familiar areas of vegetation, your

students will quickly learn that red actually represents

healthy vegetation.

Age

Grades K-12

Subjects

Art, Geography, Science, Social Studies

Duration

One hour or longer depending on the number of

images available

Skills

analysis, deciphering images, identifying similarities

and differences, interpretation, making comparisons,

map reading, observation, predicting land use trends,

spatial relationships

Key Vocabulary

aerial photo, compare, ground truth, map, observe,

remote sensing, representation, scale

Materials

Drawing materials; remotely sensed images of your area,

including a large scale aerial photo of your town (one inch

to 200 feet, or up to one inch to 10,000 feet would work—

usually available from local or city planning office, the

Soil Conservation Service, your County Extension Office,

or the U. S. Geological Survey); any other maps or

representations of your area and neighboring/connecting

areas. For younger students, an acetate overlay of the

aerial image, with important landmarks drawn on it. (See

appendices for more information on how to obtain satellite

and aerial images.)

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Where Are You From a Bird’s Eye View (continued)

Procedure

1. Mind’s Eye View: Have students work in groups to

draw a picture of the school and its surroundings as

they imagine it would look from a “bird’s eye view”.

The idea is to have your students imagine the site

from a point directly above them, but some students

may choose different perspectives. These differences

in perspective should be encouraged and should be a

point of discussion when the pictures are finished.

Have your students pay attention to detail and scale.

2. After they have drawn and labeled reasonably

detailed images, give them the aerial photos of their

town. They should identify the orientation, find their

neighborhoods, their school, parks, and other areas

and buildings of relevance to them and compare it

with their “mind’s eye view” pictures. Note - for

younger students, an acetate overlay of the aerial

image, with important landmarks drawn on it, is often

a good aid for recognizing the perspective.

3. Students should then answer the following questions

from their observation of the photo: What season

was it when the photo was taken? What time of day?

What day of the week? Does it look the same as it

does now?

4. Have your students show how they travel from home

to school, from school to a friend’s house and then

home, to the store, etc. Have your students formulate

other questions relevant to your area.

groups and with the actual aerial photos. Your students

should explain their purpose in the perspectives they

chose and look at the differences in information available.

Discuss how each perspective has its own value,

and thus, the greater the number of perspectives, the

more information is available.

Extensions

1. Follow this up with the activity “Back to the

Future”. Obtain two aerial photos of your town

which show the same area — one taken about ten

years ago and the other taken this year. Students

should compare the two photos and identify any

changes that have occurred, 10 items which are still

the same and 10 items which have changed between

the dates the two photos were taken. Follow this with

a “ground truth investigation” — visiting some of the

places that appear different in the two photos.

2. Compare the image with other representations of the

same area, such as a topographic map, city street

map, others.

3. Compare images in color infrared with black and

white photos, true color photos, X-ray images, etc.

and discuss the different kinds of information

available in these different images.

Discussion

Close this part of the activity by returning to the

students’ drawings and have them compare between

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Sandboxes & Satellites

Objectives

Students will be able to: 1) discuss how reality is

represented by maps and models; 2) recognize and

determine spatial and size relationships between objects;

3) design and create their own maps and models.

Method

Students will recreate their school grounds in a sandbox,

with clay inside a large shallow box, or with a cardboard

model. They will then photograph or video tape their

model from above and from the sides. They can also

observe the school grounds from a window on an upper

floor to gain different perspectives of the topography.

Background

It is evident that many people in our society lack basic

geographical skills. This activity will help your students

gain an understanding of topography, spatial relationships,

mapping, and modeling, helping them attain a

measure of geographical literacy. Recognizing relationships

between objects and seeing how they can be

represented in maps and models is also a first step toward

understanding how scientists use various means of

sensing our environment in order to learn more about it.

Materials

Sandbox or clay, Polaroid camera with color and black

and white film or a video camera and TV for playback,

paper, crayons, markers, pencils, a ladder, an aerial photo

of your area including the school.

Age

Grades K-12

Subjects

Geography, Social Studies, Science

Duration

Several hours or class periods.

Skills

group planning, mapping, modeling, observation,

spatial relationships

Key Vocabulary

dimension, map, model, perspective, scale, spatial

relationships, surface, terrain, topography,

3-D representation

Procedure

1. Explain to your students that they will be making a

three dimensional model of their school and its

surroundings. Team your students in small groups

and have them walk around school grounds, carefully

observing and noting the terrain, objects, and their

spatial relationships. Ask them to recreate the school

grounds in a sandbox or with clay. They should take

turns building representations of different objects

within the complete model, with the other students in

the group acting as a reality check on the builder by

asking questions such as: Is that the right scale (the

right size in relation to the other objects)? Is that in

correct spatial relationship to the other objects (in the

right place)?

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Sandboxes & Satellites (continued)

2. When the models are finished, your students should

use remote sensing (video tape or photograph) to

capture images of their model. Images should be

made from above and from the sides, changing the 3-

dimensional representation into 2 dimensions and

obtaining various perspectives. Students can also

draw pictures that represent the grounds. Use ladders

and balconies to observe, draw, and photograph the

grounds to get additional perspectives.

3. Look at an aerial photo of the area, including the

school and its grounds and compare it with the

students’ remotely sensed images. Your students

should pay attention to how their photos and maps fit

into this larger one, and gain a broader, more regional

perspective.

Evaluation

1. The groups of students should share their models and

maps, comparing and discussing them with the larger

group. Some possible questions to consider: Why

does one model look different from another if they

are based on the same reality? Why would someone

represent a particular object as bigger or smaller than

someone else? Do the photographs vary from group

to group? Why or why not? What uses might the

models and maps serve? What kinds of questions can

be answered by each of the different kinds of

representations: maps, models, and photographs?

Extension

1. This activity can be followed with an introduction

into surveying techniques:

Students (7-12 grades) can use “plane table mapping”

to make a highly accurate 2-dimensional representation

of the school grounds. This technique was used

by the British to map the entire Indian sub-continent.

Students can also use the “T-stick method” of adding

topographic relief to their maps. This technique was

developed by the Egyptians for mapping their fields

following the annual Nile floods.

Books on these techniques may be found under

surveying in the library.

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Digital Faces

How Satellites See

Objectives

Students will be able to: 1) digitize and interpret photos;

2) recognize and begin to interpret remotely sensed

images, such as aerial photos and satellite images; 3)

understand the significance of computers in satellite

imaging; 4) determine the range and resolution necessary

for given investigations.

Method

Students will bring in a photo of themselves or some

other person. Use simple, high contrast photos. Students

will “digitize” the photos using various grid sizes and

shades of gray to gain an understanding of image

resolution and how much information is needed to

answer various questions. In part two, students will

observe satellite and aerial images and extend the

understanding they have gained to interpreting these

images. It is important to follow this activity with

Zooming In and Ground Truthing Your Image.

Age

Grades 4-12

Subjects

Science, Math, Art, Language Art

Duration

At least two one-hour class periods, part may be

assigned as homework

Skills

analysis, drawing, graphing, interpretation,

observation

Key Vocabulary

analog, digital, digitize, grid, pixel, range, remote

sensing, resolution, scale

Background

Remote sensing, for the purposes of this activity, means

obtaining information about the Earth’s surface and

atmosphere from airborne or space-borne sensing

instruments. Remotely sensed images are produced at

various resolutions, depending on their intended use. The

proper range and resolution are critical if the images are

to be useful. Limited data will not answer the questions

posed, while too much data can be confusing and wastes

valuable computer time and storage space. Simply put,

enough is enough. If one wants to view a forest, for

example, one does not need, nor want, to see each tree.

There are many examples of this is daily life. When

viewing a billboard on the highway, there are various

levels of information we can gather from the sign,

depending upon our position. When far away, we can see

that it is a billboard, but we can’t tell what it says — so

there is a level of recognition, but it is not complete. At

the optimal distance, we can tell it is a sign and can read

what it says. When we are very close to it, we can again

see that it is a sign, but we cannot read it. So, we need to

be neither too close nor too far away to see the entire

message. When too close or too far away from something,

we cannot get a perspective on the whole thing

(see Goldilocks Effect activity). There is more to

interpreting images, however, than resolution. There are

also visual cues that aid our understanding. Students will

discover what some of these cues are, both in the faces

they draw and in the aerial and satellite images they

observe.

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Digital Faces (continued)

Materials

For Part I: Large (8"x10") black and white head shots of

students (pictures of themselves as younger children are

often a good subject), or full-page black and white

magazine photos of famous faces. A copying machine

that can reduce and enlarge, transparencies to make

various size grids on transparencies, graph paper, pencils.

Procedure

1. Each student selects a photo and lays a 1/8 inch or 1/4

inch grid over it. They set this image next to a piece

of 1/4 inch graph paper and set up an identical system

of coordinates on the x and y axes, one on the photo

and one on the blank graph paper.

2. The students then transfer the image onto graph

paper, simplifying the image into boxes and all of its

shades into three tones: the lightest colors become

white (leave paper blank), the middle tones become

gray (color lightly with pencil or a light color), and

the darkest third of the shades become black (color

heavily with pencil or a dark color). If a particular

pixel (box) is approximately half white and half

black, it should be averaged to become gray. If a

pixel is more black than white it becomes black. And

likewise, if a pixel is more white than black, it

becomes white. This represents a digitizing process in

three shades of gray. Note: Students should avoid

the temptation to “make it look right” by, for

example, making the eyes stand out; they should

pretend to be digitizing robots, simply averaging each

pixel, selecting the proper shade and filling it in.

Variation: Instead of using just white, gray and

black, students could use three different colors. It is

best to use colors which contrast strongly with each

other, like red, blue and green. This can be likened to

“false color” photography.

Students may find it easier to go down one row at a

time, from left to right, using a ruler, scanning and

filling in each subsequent box in the row, just like a

computer. It is also possible to let students work in

teams, one as scanner, one as digitizer. The scanner

will call out the x-y coordinates and the shade value

(white, gray, black), and the digitizer will fill in the

pixels on a separate grid.

For younger students, a numbered grid can be

prepared beforehand, with the individual grid squares

coded with different numbers which correspond to

different colors to form an image of some well know

image, such as Waldo or Mickey Mouse. Assign

colored squares to the children and have them match

them to grid locations called out by the teacher or

have them match them to coded numbers on the grid.

Then see who can first recognize the image.

3. Allow students about 30 minutes to get the hang of it

and to see how far they get. The rest may be assigned

as homework to save classroom time.

4. When they are finished, your students should observe

the image they have created and analyze it. At this

resolution, does the image offer enough information?

That depends on the questions you want to answer!

Have your students pose different questions and

consider whether their image answers each question.

For example: Is the image recognizable? Can you

tell it is a face? Can you tell who it is? Can you tell

what or who it is by viewing it from across the

classroom?

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Digital Faces (continued)

5. For the second class period, the students lay a finer -

1/8 inch - grid (more pixels) over the photo and

perform the experiment again. (If this is too difficult

for some of the younger students, say grades 4-6, you

could do this part of the activity on a board or

overhead projector with your students gathered

around to help and observe.) Another way your

students can add more information to their images,

besides changing grid size, is to add more tonal

values by making several shades of gray. The

students continue adding information by increasing

the number of tones and number of pixels until they

can tell who the person in the photo is. The students

can then analyze what questions could be answered

by the images they create at each level of detail.

Extension

Use your students’ digitized images to make a poster to

display in the school, explaining the steps and showing

the final products.

Figure 11 and 12 show the effect of digitization and how

the information content of an image changes at lower

resolution.

Figure 11: An example of a digitized photograph.

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a. b.

c. d.

Figure 12

The image on the upper left is a satellite mosaic of the Antarctic Peninsula from NOAA/AVHRR data. Each subsequent

image (b-d) shows the effect of decreasing resolution on the information content of the image.

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Zooming In

Objectives

Students will be able to: 1) discuss how reality is

represented by maps and models; 2) recognize and

determine spatial and size relationships between Earth

features and human objects, and; 3) design and create

their own maps and models.

Method

Students explore the aerial and satellite images provided

in the handbook. Using images of different resolution

and scale, they are asked to identify specific features on

each image, and compare and contrast the images.

Background

The use of aerial photography and satellite imagery

represents a major breakthrough in our ability to learn

about and understand our global environment. For the

first time in history, via imagery from space, humankind

looks upon our planetary home as a whole, recognizing

the fragility of the Earth amid the vastness of outer

space. Conspicuously absent are the political boundary

lines demarcating our self-imposed separations. This

powerful technology gives us a unique perspective,

enabling us to see the broad brush-strokes of the planet

and our activities upon it.

An important concept of remote sensing is the understanding

that different scales and resolutions provide

different types of information. Looking at a tree while

standing next to it provides an incredible amount of

subtle information about it, but very little about its

relation to the rest of the forest. An aerial photograph

provides a much better view of the forest, yet relatively

little about the single tree or the region the forest is

located in. Likewise, a satellite image provides an

incredible understanding about how the forest relates to

Age

Grades K-12

Subjects

Geography, Science, Social Studies

Duration

One hour class period or longer

Skills

analysis, interpretation, spatial relationships

Key Vocabulary

human impacts, land use, scale,

resolution, watershed

its entire region, yet provides little detailed information

about either the single forest or single tree. This concept

of scale and resolution, of course, applies to all aspects

of Earth; i.e. cities, farmland, oceans, etc. The scale and

resolution of an image determines what can be learned

from each perspective.

We recommend that you view the film or video “Powers

of Ten” by Charles and Ray Eames. This is an adventure

in magnitudes. Starting at a picnic by the lakeside in

Chicago, this famous film transports you out to the

edges of the universe and in to the micro-world of cells,

molecules, and atoms. This video is available from

Pyramid Film and Video (2801 Colorado Avenue, Santa

Monica, CA 90404; 213-828-7577), and is highly

recommended as a very easy and fun way to grasp the

concept of scale.

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Zooming In (continued)

The following images explain this concept in the same

essential way, although not to such detail. Each of these

four color images, plus the image on the cover of the

Handbook, provides an incredible amount of information,

but at different scales and resolutions. Therefore,

each image offers a different type and quality of

information. Students often find this exercise exciting,

as they zoom in closer and closer to “home.” These are a

set of generic images, culminating in a very close look at

San Francisco, California. This same exercise can, of

course, be duplicated using local images directly relevant

to your students. For assistance in obtaining such

images for your class, please contact us directly, or

consult the “Sources of Remote Sensing Imagery”

appendix in the back of this handbook. It should be

noted that these images are not true “Powers of Ten,” but

nevertheless do explain the same concept.

For the micro-scale view, it is only necessary to step

outside and ground truth your images.

A Note About the Colors

With practice it is possible to distinguish between

various land classes, such as undeveloped land, urban

and agricultural areas and to make further inferences

about remotely sensed images. The colors allow you to

appreciate and interpret the imagery, and the following

color definitions for a typical false color image will aid

you and your students in this exciting exploration.

Note: these color definitions do not work for all false

color images. (From: Educator’s Guide for Mission to

Planet Earth, by Margaret Tindal, NASA Goddard Space

Flight Center, 1978).

Red to magenta - denotes vigorous vegetation, i.e. forests,

farmlands (agriculture) near peak growth.

Pink - depicts less densely vegetated areas and/or vegetation

in an early state of growth. Suburban areas around

major cities with their green lawns and scattered trees

normally show up pink.

White - areas of little or no vegetation but of maximum

reflectance. White areas include: snow, clouds, deserts, salt

flats, ground scarring, fallow fields, and sandy beaches.

Dark blue to black - normally identifies water, i.e. rivers,

streams, lakes, the oceans. In the western U. S., however,

particularly in Idaho and New Mexico, very dense black

features are often ancient lava flows, rather than bodies of

water.

Gray to steel blue-gray - indicates towns, cities, urban

populated areas. These colors are produced by the reflectance

from asphalt, concrete and other artificial features.

Light blue in water areas - denotes either very shallow

water or heavily sedimented water.

Light blue in western areas - identifies desert scrubland

capable of supporting limited vegetation.

Brown, tan and gold - indicates areas comprised primarily

of open woodlands (piñon, juniper, aspen, chaparral).

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Zooming In (continued)

Color Image

Activities

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North and Central America

(image source: TSW)

Description

This is a satellite image of North and Central America (with

part of the Arctic) and covers an area of approximately

63,000,000 square miles. The scene was recorded by an

electronic sensor known as the Advanced Very High Resolution

Radiometer (AVHRR) onboard NOAA 9-11 weather

satellites, from an altitude of approximately 840 km (520

miles), and a resolution of 1 kilometer by 1 kilometer. This

entire image is a mosaic, or composite, of many AVHRR

images recorded between December 1985 and July 1989.

Identify major rivers and trace the watersheds of the Mississippi

and the St. Lawrence. Can your students find the

drainage system of the Colorado River, the Columbia, the Rio

Grande, or the Yukon? Locate the drainage system of your

local river. Where does it flow from and where does it go?

Locate the following coastal features on the image: Hudson

Bay and James Bay, Chesapeake Bay and Delaware Bay, San

Francisco Bay and Monterey Bay. Can they locate Long

Island, Cape Cod and Nantucket Island, or Vancouver Island?

Since the AVHRR sensor can detect wavelengths of light

beyond the visible light spectrum, information about the

Earth’s surface that is normally invisible to the human eye can

be displayed as false-color composites. Healthy, actively

growing vegetation appears in vibrant reds. This is representative

of the strong chlorophyll reflectance within the thermal

infrared wavelengths. These wavelengths are longer than the

band we experience as visible light. Water appears in black,

while desert and snow appear white.

Procedure

Beginning without the aid of a map, ask your students to

determine what features they can locate on this image. To

begin with, try to find the location of your state and your city.

How confidently can your students identify exactly where your

city is located? Why? Can they actually see your city on the

image? If an alien was looking at this image, would it be able

to detect any human activity at this scale?

Based on the information given in “A Note About the Colors,”

have your students explain the differences in color on the

image. Outline areas of different terrain and vegetation.

Separate densely vegetated areas (red) from the deserts and

mountains (white and gray). Can they locate areas with

permanent snow and ice? How can they tell these areas apart

from the deserts?

National and state boundaries are not present on this image.

Can the students identify the Canadian and Mexican borders?

How sure are they? Can they locate the Central American

countries: Guatemala, El Salvador, Nicaragua, Costa Rica,

Panama? How about Cuba, Haiti and the Dominican Republic

on Hispaniola Island, Jamaica, Puerto Rico or the Bahamas?

An excellent writing exercise is to ask the students to write a

response to the question: “What was your first impression

when looking at this image without national or state borders

marked on it?”

Some major geographic features can be identified without a

map. Where are the Great Lakes? Can your students name

them? Try to find the Great Salt Lake and Lake Okeechobee,

or Great Slave Lake, Great Bear Lake and Lake Winnipeg in

Canada. Can they pick out Lake Tahoe and Lake Powell in the

West? What size are these lakes?

Locate the Rocky Mountains and the Appalachian Mountains.

Can they distinguish the smaller mountain ranges within these

two major ranges? Can they tell higher ground from lower

areas?

Now let the students compare the satellite image with a map of

North America in an Atlas. How similar or different are they?

What differences are immediately obvious? Check the answers

students gave before with the information on the map. At this

scale they will find it difficult to locate smaller features

precisely, especially specific cities, except by finding their

geographic locations, such as San Francisco on San Francisco

Bay, or New York City at Long Island, and Detroit by Lake

Saint Clair.

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Continental United States

(image source: EROS Data Center)

Description

This is a satellite image of the continental United States.

Like the previous image, it is a false color composite

mosaic of AVHRR images. The images were collected

over a two year period from 24 May 1984 to 14 May 1986.

The spectral bands displayed are the same, so healthy

vegetation still appears in vibrant reds, but in this image,

much, although not all, water has been specially coded to

blue, making it easier to pick out lakes and waterways. The

resolution in this image is the same as in the previous

image (1 km by 1 km), because it was taken by the same

sensors. Therefore, it also contains the same amount of

information as the previous image, but it is much enlarged,

so it is possible to make out more detail. This image has

also been overlaid with the state boundaries and cropped at

the Mexican and Canadian borders.

Procedure

First of all, if you are in an area covered by this image,

locate the area in which your students live and go to

school. If you aren’t in the continental United States, have

your students pick an area about which they know something,

or would like to learn more. Can they actually pick

out your city? Could our alien now detect any human

activity in your area at this scale?

Indeed, it probably could. Very large cities, such as New

York City, Chicago, Los Angeles, etc. show up as a light

gray or blue-gray spot on the image. Small cities are

unlikely to be visible, yet it is now possible to detect

human influences on the landscape. As noted before,

healthy vegetation shows up vibrant red. In this image, it is

possible to detect human agricultural systems quite easily.

At first, point out bright red areas along major river

systems in the west, such as along the Arkansas River,

running West to East in eastern Colorado, or the area just

south of the Salton Sea, above the Mexican border with

California. There they will see the bright red which

indicates healthy vegetation in well irrigated agricultural

fields. Using these areas as clues, can they find other

areas which indicate agriculture?

What other features can your students identify at this

scale? Watersheds and mountain ranges are more

apparent, and state boundaries follow many watercourses.

Several artificial water reservoirs are also

conspicuous at this scale and resolution. For example,

using a map and the image, ask your students to locate

Lake Powell in Utah, Fort Peck Lake in Montana, or

Lake Sakakawea in North Dakota. Can they locate

natural and artificial features near your area on the

image?

As a writing exercise or discussion, ask your students to

respond to the question: “How do you think state

boundaries were drawn? Do they correspond with natural

features, or do they appear to have been made with other

considerations in mind?” For example, ask them to

compare the state boundaries of Virginia with those of

Colorado.

The student should be able to outline major watersheds

and differences in color and attempt to explain these

differences. For example, why is the western region of

the United States blotched with gray and white, while the

eastern region is so red? What explains the bluish color

of southern Florida, or the bright white patterns in

Colorado, Wyoming, Idaho and other western states?

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San Francisco Bay Region

(image source: ERIM)

Description

This view of the Bay area around San Francisco, California

is an enlargement of part of a Landsat multispectral

scanner (MSS) image taken from an altitude of 700 km

(438 miles), in the late 1970s. The MSS sensor records

electromagnetic radiation in the green and red (visible

light) and two infrared spectral regions and has a resolution

of about 80 meters (250 feet). MSS images are more

than 150 times sharper than those of the AVHRR and a

wealth of detail is available. In fact, linear features as

narrow as 10 meters are sometimes visible where they are

in sharp contrast with their surroundings (e.g. bridges over

water or dirt roads passing through dark brush). Like all

the images in this book, this one is a false color infrared.

Procedure

Familiarize yourself with the San Francisco Bay area by

checking conventional maps or atlases and other source

materials and use the following information to explore the

image with your students.

Urban development, which is indicated by gray to bluegray,

is prominent in this view and reveals several well

known cities: San Francisco, on the northern tip of the

peninsula; Oakland, across the straits from San Francisco;

and San Jose, at the southern tip of the Bay. The Golden

Gate Bridge connects the Presidio in San Francisco with

the Marin Headlands to the North. At least three other

bridges are visible in the image: the Richmond-San Rafael

Bridge across the San Pablo Strait; the San Francisco -

Oakland Bay Bridge (which partly collapsed in the

earthquake of October, 1989) that also connects with

Treasure Island ; and the San Mateo Bridge across the

southern Bay. Landfills and salt evaporation pans show up

emerald green in the south part of the Bay and at least

three airports, including the NASA base at Moffett Field,

are also visible.

The scale of this image can be estimated by taking a

measurement of an object of known size and then using it

to calculate the scale. Once the scale is known, it is equally

possible to determine the approximate size of objects in the

image. For example, using the Golden Gate Bridge as a

yardstick (a six-lane highway, 2,824 meters or 3,089 yards

long), measure the size of various features. (e.g., How

long are the other bridges? What is the area of this image?

How long is Golden Gate Park?)

The region includes a diversity of farm products, including

lettuce, tomatoes and grapes in the Santa Clara, Salinas and

Great Valleys. The Sacramento Valley is used almost

entirely for rice, cotton, barley and other cash crops. Since

this image was recorded, this area has suffered a terrible

drought beginning in 1986. Knowing this, how would this

image be different if taken today?

Geologically, the area contains the Calaveras and San

Andreas faults. The infamous San Andreas fault can be

seen south of San Francisco where the long, linear

reservoirs highlight it at the base of the Santa Cruz

mountains. Also evident are the intricately folded coastal

mountains with their many watersheds. The Sacramento

River enters the Bay in the northeast corner of the image.

The bay also contains several easily identifiable islands.

Can your students find Angel Island, Treasure Island, or

notorious Alcatraz? Just north of the Golden Gate Bridge

lies Muir Woods, named for the famous naturalist; a

national monument protecting the Redwood Forest. The

Santa Cruz mountains contain the southern-most Redwood

forest, indicated by the deep reds, along the California

coast. The hills to the north, south and east of the Bay area

support California Oaks and Evergreens, mixed with

Chaparral in places. Recent fires in the Chaparral have

caused the loss of many homes.

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The Presidio, San Francisco, California

(image source: Eros Data Center)

Description

This final image is a color infrared (CIR) photograph taken

from an aircraft flying at an altitude of 20, 000 feet in June

of 1987. It shows a very detailed view of the northern area

of San Francisco and the Golden Gate Bridge. Such aerial

photographs reveal an enormous amount of detail about a

very limited area. Similar color infrared photos are

available for all of the United States, including the area

where you live, and are suggested for use with this

handbook.

Procedure

At this resolution and scale, buildings, cars on the streets

and parking lots, ships in the bay, and individual trees in

the parks are clearly visible. Can your students identify

Fort Point, at the base of the Golden Gate Bridge? Can

they pick out the Presidio Army Golf course? How can

they tell it is a golf course? The San Francisco Palace of

Fine Arts is a large crescent shaped building. Have the

students locate it on the image.

Ask the students to become very specific about what they

can see. For example, using the Golden Gate Bridge (2,824

m. long) as a measuring stick to determine scale, ask your

students to estimate the area of Alcatraz Island and the

lengths of some of the ships in the image. How many

kilometers to the east of the Golden Gate Bridge is

Fisherman’s Wharf (at the eastern edge of the image). The

streets are very evenly spaced, so what are the dimensions

of a city block in the city of San Francisco? What proportion

of the city is made up of parks and green spaces? Can

they make out baseball diamonds or football fields? What

keys can they use to determine these features? The

University of San Francisco is on the image—can they find

it? What cues did they use? It is possible to estimate the

time of day at which the photo was taken from shadows of

tall objects, such as buildings or the Golden Gate Bridge.

What can your students tell about wave conditions and the

direction the wind was blowing when this photo was

taken?

To the North of the Golden Gate Bridge is the Marin

Peninsula and the Muir Woods National Monument. Do

the areas of San Francisco and the Marin Headlands appear

to be flat or mountainous? Ask your students to compare

the woods with the vegetation visible within the city. Can

they tell the difference between dense forests and grassy

areas? Have them compare the golf courses with parks of

the city and the National Park. Based on the information

given in “A Note About the Colors”, have your students

explain the differences in color on the image, especially

the different shades of red and pink. What might explain

these differences? Remember that California has been

experiencing a prolonged drought. On sheets of acetate,

have the students outline areas of different terrain,

vegetation, urban areas, and major highway corridors.

Given their knowledge of San Francisco based on these

images, where would your students like to live?

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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Handbook Cover

Turkey Point and the Everglades, Florida

(image source: ERIM )

Description

The striking image on the front and back cover of this

Handbook is a Landsat image showing the Turkey Point

area, south of Miami, and a portion of the Everglades.

The scene was recorded by an electronic sensor known as

the Thematic Mapper (TM) on board Landsat 5, at an

altitude of 700 km (435 miles), with a resolution of 30

meters (98 feet). Note the difference in resolution

between this Landsat TM image and the Landsat MSS

image of the San Francisco Bay area.

Exploring the Image

Use this image with your students to explore an area very

different from that of the San Francisco Bay area. Ask

them to use the skills they have developed to interpret

this striking image. What conclusions can they draw

about the nature of city development and natural systems

in this area? What would be the consequences of a

radiation leak at the Turkey Point nuclear power plant to

the residents of the area? What effect will further road

building and development have on the Everglades? What

effect would rising sea levels, associated with global

warming, have on these communities?

This area of Florida encompasses climates, vegetative

habitats, and economic pursuits not found elsewhere in

the continental United States. Most of the land surface is

at or near sea level, reflecting its youthful age in terms of

its emergence from the seas that once covered all of

mainland Florida.

This image contains a number of interesting natural and

artificial features for your students to examine. In the

Everglades, for example, vast expanses of sawgrass (the

darker colored areas) are interspersed with hammocks

(“tree islands”) - slightly higher land covered with

hardwood trees. The splotches of intense red occurring in

long, arcing patterns represent the hammocks and show the

natural flow of water through the Everglades. Mangrove

swamps are confined to the coastal areas and show up

brilliant red against the dark blue of the ocean waters.

Note, too, the light blue streaks that delineate the great

coral reef that is part of the Florida Keys. Key Largo is the

red island off the coast.

The image clearly shows how humans are encroaching on

the Everglades: the many dark blue inland areas, surrounded

by white, are gravel pits which provide landfill

and construction materials for new developments. The

regular patchwork of red, gray and white is the development

of new areas south of Miami. The grid of canals

forming the cooling system for the Turkey Point nuclear

power plant on Biscayne Bay is strikingly apparent, as are

the runways of Homestead Air Force Base to its northwest.

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Zooming In (continued)

Evaluation

Before you leave the color images, have your students go

back to the previous images and report whether they can

now find more detail in the satellite images than they had

found during their first investigations. As a writing

exercise, ask the students to answer the questions: 1) How

does comparing between images of different scales and

resolutions add to your ability to interpret all of the

images? 2) How would being able to ground truth the sites

on the image affect your ability to correctly interpret the

images?

Conclusion

These images are beautiful and fun to look at, but so what?

Why is remote sensing important?

Remote sensing provides a unique tool for the study of

both the Earth as a whole and its respective parts. The

applications are almost limitless, as almost every field and

every discipline can potentially benefit from its use. For

example, in Earth Science, one can identify and study

drainage patterns, glaciers, volcanoes and their impacts,

and map surface and tectonic features. In Environmental

Studies, one can identify and map categories of land use,

study human impacts on the environment, and observe

change over time. In Social and Urban Studies, remote

sensing can be used to study urban size and function, urban

form and structure, significant social issues, historical and

political events, and economic activities.

A vast amount of information is already available for your

locality using this technology. It is certainly possible for

you and your students to study and track many aspects of

your area; development, habitat, population increase,

agricultural seasons, etc., just to name a few. Similar data

exists for almost every other point on Earth. This allows

you to make the connection from local conditions to

regional and global perspectives. It also makes discussion

of environmental issues far more meaningful; i.e. studying

a satellite image of rainforest deforestation.

For more information about the many applications of

remote sensing, please refer to the “Image Application

Chart,” the “Bibliography of Suggested Reading,” and the

“Sources of Remote Sensing Imagery” found in the back of

this handbook. For assistance in obtaining images for your

class, please contact AGCI directly, or consult the

“Sources of Remote Sensing Imagery” mentioned above.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Ground Truthing Your Image

Objectives

The students will be able to: 1) demonstrate an understanding

of how resolution affects information content

on remotely sensed images; 2) relate their digitizing

activity to the information content of the satellite image;

3) interpret remotely sense images and verify them

using ground truthing techniques; 4) relate remote

sensor resolution (pixel size) to information content; and

5) gain an understanding of the information content of

different kinds of remote sensing imagery.

Method

First, the students examine aerial or satellite images of

your school area in much the same way that they

analyzed the digital faces they created. How many

pixels? How many tonal values? What kinds of

questions can be answered from the images at the given

resolutions? What kinds of questions would require

greater resolution? Less resolution? What resolution is

needed for what studies?

Second, students use the image of the area surrounding

your school to identify features as specifically as

possible (i.e., the school playing fields, a stand of pine

and oak trees near the school or individual trees, a pond

in a neighborhood park, grocery store parking lot with

how many cars, dirt or paved roads, etc.)

Third, the students take field trips to “ground truth” their

interpretation of the images. During these field trips,

students will classify as specifically as possible the areas

they visit. For example, they should identify the

structure and species of trees in a wood, or the amount

of bare soil and grass on the playing field, or whether a

parking lot is asphalt or concrete.

Age

Grades 4 -12

Subjects

Geography, Science, Math

Duration

Two or more class periods

combined with field trips

Skills

analysis, image interpretation,

soil and plant identification

Vocabulary

botanical names, clues, cues, keys,

vegetative cover

Finally, the students will mark out pixels on the ground

which correspond to the sizes of actual image pixels.

They will also compare their view of the pixel and the

image the satellite scanner or aircraft camera records

(bird’s eye view).

Materials

Aerial photos of the vicinity of the school; satellite

images of Earth, preferably including the area of the

school (the images provided with this handbook provide

good starting examples of different views of the same

area); magnifying glasses (2x, 5x and 10x); photographs,

magazine and newspaper pictures. For the field trips,

bring plant identification books (or a local naturalist),

some long tape measures (100 meters if possible), and

journals or notebooks to record the observations.

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Ground Truthing Your Image (continued)

Procedure

1. Look at aerial photos of the area surrounding your

school. Aerial photos are another kind of remote

sensing, taken closer to the subject than satellite

images. Identify neighborhoods, the school and

grounds, bodies of water, highways and other

landmarks. Students may wish to compare a current

aerial photo with one taken many years ago. Observe

natural and human-caused changes in the landscape

and discuss these changes. Do the same with satellite

images. How do the two images differ?

2. Look at all three types of images you now have

before you: the student digitized images, the aerial

photos, and the satellite images. What are the visual

“keys”, “clues” or “cues” that you use to help

interpret the images?—Keys unlock things; clues are

bits of evidence that help solve a puzzle; cues are

information that prompt understanding. You may

notice that eyes are a key in recognizing a face,

bodies of water are keys in aerial photos of a

landscape, and bodies of land and water are keys in

satellite images. Students should identify as many

features as they can and be specific about what these

features represent (i.e., park, duck pond, the shopping

mall at 43rd Street with parking for 5000 cars, a little

league baseball diamond, etc.). Students can “read”

the images and discuss what helps them understand

and interpret what they are seeing.

3. Use the magnifying glasses to compare regular

photographs to magazine and newspaper photos under

different magnifications. At between 5x and 10x

students should start to see the dots of the newspaper

and magazine images. These are similar to the pixels

of the digital satellite images. Is the printed page

higher or lower resolution than a photograph? Compare

some color prints using the same magnifications as

above. You will see much less graininess. Photography

relies on minute chemical crystals which react to

different wavelengths of light. Faster speed films (such

as ASA 400 or more) are visibly more grainy than films

which need more light (ASA 25).

4. Take a field trip to some of the sites identified on your

images. Ask the students to describe as exactly as

possible the features which they had identified on the

images. Have them examine the structure of objects,

such as the composition of a forest, meadow or park.

Have them identify some plants to genus or species

level and ask if this could be determined from their

images. How accurate were they? Ask them to compare

what they see while standing on the ground with what

the satellite or aircraft viewed. How important is

“ground truthing” to accurately interpreting an image?

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Ground Truthing Your Image (continued)

5. While outside on the field trip, have your students use

the measuring tapes to map out “real” life-sized pixels

on the ground which correspond to pixel sizes from

satellite images:

SATELLITE SENSOR RESOLUTION

SPOT panchromatic (black and white) 10 m x 10 m

SPOT multi-spectral 20 m x 20 m

Landsat Thematic Mapper (TM) 30 m x 30 m

Landsat Multi-Spectral Scanner (MSS) 80 m x 80 m

NOAA Advanced Very High Resolution Radiometer (AVHRR) 1 km x 1 km

6. Have the students digitize a number of these different

sized pixels according to the most common component

of each pixel, just as they did in part I of this activity.

They will have to decide what is the most common

reflective surface in the Pixel. What information can

still be gained from a pixel of 10, 20, 30, 80, or 1000

m 2 . What information would be lost when averaging

the reflected light from the pixel groups your students

identified?

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Investigating the Invisible

Objectives

Students will be able to: 1) discuss the existence of

invisible phenomena; 2) develop ways of verifying and

measuring their existence.

Methods

Students will discuss and research different invisible

phenomena. They will then test and verify the existence

of selected invisible phenomena by using measurement

or detection devices and track them on a regular, longterm

basis.

Background

Many phenomena which are remotely sensed are not

visible — examples include ozone concentrations in the

upper atmosphere, temperature, and ultraviolet radiation.

Students can use this activity to learn about the tools for

sensing such phenomena in their own environment, and

to consider the significance of such measurements.

Students should also use this exercise to contemplate

how they define “invisible.” For example, if an

organism or object is too small to be seen with the eye,

but can be seen with the aid of a microscope, is it

invisible? Some things are visible from one perspective

or scale, but not another—like Earth’s atmosphere,

which can be seen from space, but not from the surface.

Water can be invisible in its vapor phase, but visible in

its liquid phase. Temperature, which is easily felt, is

visible only indirectly, as in its effect on a thermometer,

or ice forming on a pond.

Age

Grades 4 - 12 , adapted for each grade level

Subjects

Science, Social Studies, Math, Language Arts

Duration

Approximately two class sessions, plus a few

minutes each day to measure and record data

Skills

building, charting, collecting and recording data,

computing, crafting experiments, graphing,

measuring, observation, planning, research,

word derivation

Key Vocabulary

concentration, evidence, invisible, long-term,

measurement, ppm (parts per million), seasonal,

sensor, short-term; prefixes such as micro, tele,

thermo; and suffixes such as meter, scope

Materials

Research library; instruments such as a thermometer, an

ultraviolet sensor, infrared film, a light meter, gas

sensors, filters, anemometer, decibel meter, radondetecting

test kit, microscope, and telescope, graph

paper, paper, pencils.

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Investigating the Invisible (continued)

Procedure

1. Ask your students to think and talk about what

“invisible” means. For example, how do they know

that something exists if they cannot see it. Have your

students form small groups to choose one “invisible”

phenomenon. These groups should then research and

figure out how they can verify its existence.

2. Students examine the measurement tools and

consider what they are called. This provides a good

lesson in language and root words. Roots such as

meter and scope are paired with thermo, tele, micro,

etc. When students learn some of the basic meanings,

they can figure out for themselves what related, but

unfamiliar, words mean.

3. The groups should use their tools to measure their

invisible phenomenon every day for a designated

period of time, preferably long-term. Have them

chart and/or graph their data and post it in a special

place in the classroom designated for the “Daily

Invisible Data Set.”

4. In some cases, the students may be collecting the

only daily information on a particular subject and it

may be of interest to the wider community. For

example, if students measure ultraviolet-B, they

could issue UV-B alerts the way weather reporters

issue smog alerts. They could warn fellow students

or even the entire community (via school newspapers,

public access cable, local newspapers, etc.) of

an increased need for hats, sunscreens and sunglasses

on high UV-B days. They could visit tanning salons

and measure the UV-B output of the machinery to

determine if it falls within federal guidelines.

5. Students studying radon could test radon levels in the

school basement, in their classroom and in their

homes. They could read recently published information

about radon and the controversy surrounding its

relative danger.

Discussion

Bring the different groups together to discuss their

experiences and share their data. Let them present their

measuring devices to the other groups and explain how

their device functions and how it verifies the existence of

the phenomenon they are measuring. Bring up the topic

of the nature of “invisible” phenomenon and discuss how

their perception has changed.

Extension

1. Students collect their “Daily Invisible Data Set” and

enter it into a computer which is networked (through

EcoNet or other computer network) with other

schools around the country or the world. The students

compare their data with that coming from other areas,

gaining a larger perspective on invisible phenomena.

A forum for making, testing and sharing data from an

inexpensive ozonometer is available on EcoNet.

Plans for making a low cost UVB meter are available

in the “Amateur Scientist” section of the August

1990 issue of Scientific American.

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How When Affects What: Part I

When You Look, Where You Look

Objectives

Students will be able to: 1) gather and record visual and

written data from their surroundings; 2) show how the

specific time of data collection, or the sampling window,

chosen for examination can affect an outcome, sometimes

resulting in false conclusions.

Method

Students will photograph and/or count the number of

people in the public areas of the school, such as hallways,

the cafeteria, the gymnasium, etc. They will also

consider various “windows” or periods of time within

which to examine data. They will discuss what conclusions

might be drawn from their data sets and why these

conclusions might not be accurate. In part two of this

exercise, students will then examine global change data,

a graph of global temperatures, and extend their understanding

of how time of data collection and window of

the data set affects conclusions. Variation: It may also

be suggested to the students that they measure and

compare daily temperatures instead.

Age

Grades 7 -12

Subjects

Science, Social Studies, Math

Duration

One class period to prepare, several days of “out of

class” data acquisition, one class period

for discussion

Skills

analysis, calculating, data interpretation,

observation, pattern recognition

Key Vocabulary

climate, data, data set, natural variability, pattern,

variability, weather, window

This activity should be followed up with Part II, and

with Part III.

Background

In global change research, as in any scientific research,

the timing and duration of data collection, and the

window of the data set are of critical importance in

reaching accurate conclusions. This is best illustrated by

seeing how “truth” can easily be distorted by isolating a

part of the complete data set or by collecting data at a

particular time. Issues such as natural variability often

come into play, and it is important to evaluate cause and

effect.

Materials

Camera and film (preferably Polaroid or video camera

for instant results), paper, graph paper, pencils and pens.

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How When Affects What: Part I (continued)

Procedure

1. Explain the purpose of this activity to your students

and have them choose a public area of the school

(hallways, cafeteria, gymnasium) as their subject of

study. They should photograph (or count the people)

in these areas from above (from a window, high up in

a nearby building, etc.) at various times of day—say

8 am, lunchtime, and on different days of the week—

and count the students that appear at each time. They

can choose some special times to collect data.

2. The students should then graph their data and

describe what they have learned about the phenomenon

they measured—such as average number of

students counted—based on when the observations

were made.

Extension

1. Ask the students to design a sampling schedule which

would help avoid gross distortions of reality, but

which do not require continuous sampling.

2. Have students bring in examples from articles in the

press which demonstrate the effect that how and when

data is collected has an impact on the conclusions

drawn.

Discussion

Ask your students to examine their data and pose

questions that can be answered by evaluating that data.

How would someone interpret the data if they did not

know where and when it had been collected? What

kinds of conclusions can be drawn from the information

collected? How did the time of collection affect the

answers to the questions posed? How did the window

selected affect the outcomes? How might the data be

interpreted or misinterpreted? Students can come up

with conclusions they know are false, but which can be

supported by their data sets. Have your students discuss

ways in which information might be unintentionally

misread or intentionally manipulated.

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


How When Affects What: Part II

Is it Getting Hot or Not?

Objective

Students will be able to: 1) critically interpret graphical

data; 2) evaluate and discuss the difficulties inherent in

interpreting and forecasting long and short term trends.

Method

Students will extend the understanding gained in the first

part of this activity (counting students in the school) to

global mean temperature change. They will see how the

sample or window they choose to examine effects the

outcome of their study.

Background

During the past 20 years, much attention has been given

to the potential climatic effects of increasing concentrations

of atmospheric greenhouse gases. Much work has

been performed during this period and researchers have

gained important new insights from these studies. The

graphs on the following pages show that there was little

trend towards increasing or decreasing temperature

during the 19th century, a marked increase of about 0.5 o

C from about 1910 to 1940, followed by a period of very

erratic and dramatic temperature fluctuations from 1940

to 1970, and followed again by a sharp increase in

temperatures to the present. The 1980s were a decade of

unprecedented warmth, with 1990 the warmest year since

comparable records began in the middle of the 19th

century. All six of the warmest years in the global record

have now occurred since 1980, and after corrections for

the influence of El Niño ( a warm current in the Pacific

ocean which has a powerful influence on the world’s

climate), every year since 1985 has shown an increase in

temperature.

Some scientists see a trend of increasing global temperatures

in this data. James Hansen and Sergij Lebedeff, of

NASA’s Goddard Space Flight Center, reported in 1988

Age

Grades 7-12

Subjects

Math, Science, Social Studies

Duration

One or two class periods

Skills

analysis, data interpretation, forecasting

Key Vocabulary

long and short term observations, sample size,

trend, window of observation

that the global surface air temperature in the 1980s were

the warmest in the history of meteorological records and

that the four warmest years on record were all in the

1980s. Other scientists emphasize the large amount of

variability in the global temperature record, and argue

that the globe has not warmed as much as predicted by

climate modelers, and thus there is no evidence of global

warming. Against this backdrop of high annual temperature

variation and inconclusive trends, government policy

makers must decide whether to take action to reduce

greenhouse gas emissions or not. Some policy makers

oppose any specific timetables for combating global

warming, citing lack of agreement among scientists on

the problem. Others call for the establishment of specific

targets for cutting the pollution that causes greenhouse

gases (principally carbon dioxide and methane).

This exercise is an opportunity for your students to view

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How When Affects What: Part II (continued)

the data, discuss the issue, and draw their own conclusions

using the actual data which is the basis of the

controversy. This data was compiled by P.D. Jones,

T.M.L. Wigley and P. B. Wright from the Climatic

Research Unit of the University of East Anglia in

England.

Materials

Four graphs of global mean temperatures: the first from

1882 to 1894; the second from 1944 to 1956; the third

from 1978 to 1990; and the fourth from 1854 to 1990,

presented on following pages.

Procedure

1. Divide the class into four groups, or subsets of four

groups. The groups should be kept separate so they

cannot share data and gain information from the

graphs of other groups. Give each group (or subgroup)

a copy of one of the four temperature graphs.

Students will study their sample of global mean

temperatures and observe how readings fluctuate

from year to year, over two to several to many

decades. By looking at their samples, they should

theorize whether there is evidence that global

temperature was rising, falling, or remaining

constant. They should be able to back up their

conclusions with the data from their sample graph.

2. After the students have spent some time studying

their graphs, ask them to project what global surface

air temperature will be 10, 20 and 50 years into the

future.

3. Have each group, beginning with the first temperature

chart (1882 to 1894), present their predictions for

average global temperatures 10, 20 and 50 years in

the future. The last group to report should be the one

with the 138 year chart.

4. With the 1854 - 1992 graph, let the students from the

first three groups compare their estimates with the

longer term graph.

Discussion

1. Compare the four sets of predictions and consider the

reliability of each. Discuss the implications of basing

conclusions on limited data and the patterns that

could be inferred from considering each of these

subsets. The pitfalls of basing conclusions on limited

data sets should become obvious.

2. How much data is needed to make reliable predictions?

Have students develop a list of things they

would need to find out in order to prove that their

projections were valid.

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How When Affects What: Part II (continued)

0

Global Mean Temperature

Temperature Change (˚C)

-0.1

-0.2

-0.3

-0.4

1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894

Year

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How When Affects What: Part II (continued)

0.2

Global Mean Temperature

Temperature Change (˚C)

0.1

-0.1

0

-0.2

1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956

Year

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How When Affects What: Part II (continued)

Global Mean Temperature

0.4

Temperature Change (˚C)

0.3

0.2

0.1

0

1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990

Year

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How When Affects What: Part II (continued)

1990

1980

1970

1960

1950

Global Mean Temperature

1890

1900

1910

1920

1930

1940

Year

1880

1870

1860

0.4

0.3

0.2

0.1

0.0

-0.1

-0.2

-0.3

-0.4

-0.5

-0.6

Temperature Change ˚C

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How When Affects What: Part II (continued)

Extension

Perhaps the 138 year sample that we called the “big

picture” is but a blip on the larger time scale and is

really too small a sample. Why might this statement

be true or false for human purposes? What is the time

scale of concern for human study? If the temperature

rises or falls, is the Earth itself in peril or is human

civilization as we know it in peril?

Temperature Change (˚C)

(a)

Previous ice ages

Last ice age

800,000 600,000 400,000 200,000

Years before present

Discuss how much data is enough to be reliable while

comparing the four different data sets, the 136 year

graph, the 1,000 year temperature graph, the 10,000

year temperature graph and the 1,000,000 year

temperature graph.

Temperature Change (˚C)

(b)

Previous ice ages

Holocene maximum

Last ice age

Little

ice

age

10,000 8,000 6,000 4,000 2,000 0

Years before present

Temperature Change (˚C)

(c)

Medieval

warm period

Little ice age

1000 AD 1500 AD 1900 AD

Years before present

Figure 12: Schematic diagrams of global temperature variations

since the Pleistocene on three time-scales; (a) the last million

years, (b) the last ten thousand years, and (c) the last thousand

years. The dotted line nominally represents conditions near the

beginning of the twentieth century. From: 1989/90 UNEP

Environmental Data Report.

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How When Affects What: Part III

Local Temperatur es, Global Changes

Objectives

The students will be able to: 1) monitor daily temperatures

and average daily minimums and maximums; 2)

explain factors which affect the temperatures they take;

3) compare their temperature record with local weather

station readings; 4) compare their data with that of the

average global temperature used by scientists to monitor

for global warming.

Method

Students will set up at least one temperature monitoring

station at the school and take daily minimum and

maximum temperature readings. The minimum and

maximum daily measurements will be averaged to give a

rough estimate of the mean (average) daily temperature.

Daily temperatures should be averaged each week, and

weekly temperatures averaged each month, and finally,

monthly temperatures will be averaged each year. These

data will be displayed on separate graphs showing the

long term variations in temperature for your school.

These local average temperatures can be compared to the

global average temperatures for the period of 1854 to

1990 found in the appendix. Finally, updated monthly

global and regional average temperatures can be obtained

from the Aspen Global Change Institute, to make an upto-date

temperature graph of global temperatures as

recorded by satellite. If available, a weather or data

logging system could be used to automate the data

collection process once the students have learned to carry

out the procedures manually.

Background

During the last 20 years, much attention has been given

to the potential climatic effects of increasing concentrations

of atmospheric greenhouse gases (see the Global

Change Primer). In order to isolate the “greenhouse

signal”, or that part of the climate change which indicates

Age

Grades 7-12

Subjects

Science, Math, Social Studies

Duration

Two class periods to set up, followed by daily monitoring

and weekly analysis

Skills

averaging, data recording, analysis and interpretation,

graphing, temperature and weather monitoring

Key Vocabulary

anthropogenic, average and mean, degrees Celsius and

Fahrenheit, global warming, temperature graph

anthropogenic global warming, it is necessary to identify

what temperature changes would have occurred naturally

and which may be due to human activity. Fortunately,

temperature records have been kept since about the

middle of the last century. This historical data set is vital

to identify whether or not human activities are causing

global warming.

Taking the Earth’s temperature, however, is a complex

and difficult task and many methods have been used over

the years. For example, one important source of information

comes from sea surface temperatures taken by ships

crossing the oceans. Much of the older data came from

sea surface temperatures measured by hauling canvas

buckets of water aboard ships. Later the canvas bucket

were replaced by wooden buckets, and now sea temperatures

are measured as water is brought on board to cool

the ships’ engines. These three techniques yield different

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How When Affects What: Part III (continued)

temperatures which must be accounted for. This activity is

designed to give students an appreciation of this task of

measuring average global temperatures. An excellent

review of the process of analyzing global temperatures can

be found in Global Warming Trends, by P.D. Jones and

T.M.L. Wigley in Scientific American, August 1990. The

Jones and Wigley data are presented in the appendix of

this handbook for use by your students.

Materials

Minimum-maximum thermometer, hand-held thermometers,

data sheets for recording time, date, minimum and

maximum temperatures, weather conditions and other

relevant data.

Procedure

1. Students should be given some background on the topic

of global warming, as presented in the Global Change

Primer. Older students should be encouraged to

research the topic, especially how average global

temperatures have been calculated.

2. Students should then be told that they will have an

opportunity to measure local temperatures and compare

them with the local newspaper, radio station, and

weather station reports. They should decide where to

place a maximum-minimum thermometer to get

representative readings at the school. (Care must be

taken to keep it out of direct sunlight and away from

other areas which might artificially affect the temperatures.)

If possible, multiple stations could be set up,

including at the students’ homes for comparison.

3. A list of student data recorders should be established,

with student teams spending at least a week each

monitoring the thermometers, recording the daily

temperature ranges, calculating the daily average and

graphing the results. Weekly and monthly, the data

should be averaged and reported to the entire class.

4. A separate team of students should obtain daily or

weekly data from your local weather service and graph

this on the same graph, and in a similar manner (i.e.

daily, weekly, monthly and annual) as the school

recorders.

5. The data for the 1854 to 1990 global average temperature

is listed in the appendix. Students should use this

data as an exercise in graphing data. The results should

be the same as in the temperature graph in How When

Affects What: Part II. The students graphs of global

mean temperatures should be displayed in a spot for the

entire school to see and where they can be compared

with the local temperature graphs.

Extensions

Monthly global temperature data recorded by the Microwave

Sounder aboard the TIROS-N satellite, and

compiled by Roy Spencer and John Christy, are now

available. The satellite data record extends back to 1979

and represents the most comprehensive recent temperature

record to date and provides quasi-global coverage each

day. The satellite measures tropospheric temperatures to an

accuracy of 0.01 ˚C. Current data and the annual averages

for the northern and southern hemispheres, and for the

globe as a whole, are available on InterNet or from the

Aspen Global Change Institute. Please contact us if you

would like to use this information with your class.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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Dust Busters

Objectives

Students will be able to: 1) discuss and explain the

presence of particulate matter in the air; 2) identify

particles collected from the air around them; 3) explain

what they are, where they come from, and what their

effects are on the health of humans, wildlife and vegetation.

Method

Students will collect samples of particles in the air on

simple slides they make themselves. They will classify,

count and chart their findings, draw conclusions, make

predictions, and compare their findings to other available

data.

Background

The air around us is anything but “pure”. The air we

breathe contains many particles which can be readily

sampled and identified. Some of these particles, such as

plant pollen, can cause human discomfort in the form of

allergies, or “Hay Fever”. Other particles may be dust or

lint, which may also cause allergies. The EPA has set

standards for acceptable limits of dust pollution. Surprisingly,

this is often worst in the winter as a result of

sanding icy or snowy roads. In many cities, daily

newspapers and radio and television stations announce

pollen counts and allergy alerts. Allergists, medical

doctors who treat allergies, have developed a simple, yet

effective, method of measuring the presence of particulates

in the air. This same method will be used here.

Age

Grades 4 -12

Subjects

Science, Social Studies, Math

Duration

One class period to set up, should run through year,

graph against seasons

Skills

calculating, charting, classification, data collection,

evaluation , prediction, research

Key Vocabulary

air quality, atmosphere, data, particles, particulates,

pollution, prediction, sample, seasonal variation

Materials

Microscope slides, petroleum jelly or clear adhesive tape,

magnifying glasses and microscope, Eosin, Methyln Blue

or Iodine for staining the particles, paper and pencils,

data on particulates in your area (available from your city

air quality control office, or from an allergist).

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Dust Busters (continued)

Procedure

1. Students make “sticky slides” by coating them with

petroleum jelly or wrapping the slides with clear,

adhesive tape with the sticky side out. The slides

should be placed in various locations around the

classroom, school and grounds, or taken home to

collect samples of particles in the air. In each

location, place one slide vertically and another

horizontally.

2. Collect and view the slides with a magnifying glass

and microscope. The students should design a system

to classify, count, and chart all visible particles.

Shape, size, and composition are some of the

elements students can use to classify the particles.

Older students should be allowed to invent their own

means of cataloging their data, while younger

students (grade 4-6) should be assisted in setting up

their charts. Students should check results seasonally,

with varying temperature, before and after rain

storms, and with other variables. Account for and

discuss variations and reasons for them. Discuss all

data collected and attempt to draw conclusions based

on evidence.

Discussion

Bring in and discuss reports on pollen and dust from the

newspaper, radio or television, and other available data

on particulates in your area. Compare those results with

those obtained by the class. Make predictions about

trends such as increasing or decreasing numbers of

certain particles. Discuss what factors might affect such

trends and what impacts various types of particulates

might have on humans, wildlife, and plant life in the

environment.

Extension

1. Develop and graphically display a weekly or

seasonal “particulate index” for your school.

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Dead Right, Dead Wrong

Objectives

Students will be able to: 1) make informed decisions

regarding the current global warming debate; 2) present

evidence to support their views on the issue.

Method

Students will research and evaluate information about

global warming, identify decision-making criteria for

action or lack of action, and decide what level of

certainty is sufficient to take action. They should debate

the issue of when we know enough to act, based on the

results of their research.

Background

A recurring question regarding society’s handling of

scientific problems is: how certain must we be of a bad

outcome in order to take action to prevent it? How

much evidence is enough to cause us to change our

ways, especially if the changes are believed to be

difficult and expensive?

One way of looking at it is to draw an analogy to buying

insurance. Even though there is a very low probability

that my house will burn down, I purchase fire insurance

to protect myself and my family from being devastated if

fire does strike. It costs money for this protection, and

some might say that since the probability is so low, the

money is wasted, but most prudent people do carry

insurance.

Applying this logic to increasing global temperatures,

even if we are not certain that it will occur (even, in fact,

if the probability were low that it would occur), some

people would consider it prudent to take action to

Age

Grades 7-12

Subjects

Science, Social Studies, Math

Duration

Two or more class periods

Skills

critical thinking, debating, organizing,

predicting, research

Key Vocabulary

criteria, prediction, probability, variability

prevent or reduce it, even if it cost something. This is

especially true since the effects of global warming, if

they occur, could be cataclysmic.

Another very significant factor in this debate is that if

we wait for absolute certainty that there is a distinct

warming trend, it would then be too late for our actions

to make much of a difference. If we wait 50 years for an

undeniable signal without changing our output of

greenhouse gases, in the meantime carbon dioxide levels

will have doubled, methane levels will have more than

doubled, and we will be dead right or dead wrong—it

won’t matter.

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Dead Right, Dead Wrong (continued)

Materials

A library with periodicals and reference books. Good

sources include recent editions of the major encyclopedias,

especially their annual updates, and science

magazines such as American Scientist, New Scientist,

Scientific American, and Science News. Newspapers

and weekly news magazines are a good source of

material concerning the political debate surrounding

global warming, as well as other global change issues.

Procedure

1. Do we have enough evidence for global warming to

take action to prevent or reduce it? Divide your class

in three sections, with one smaller group of 5 to 7

students to act as judges and referees between the

two other larger groups. The first large group will

research and debate on behalf of taking immediate

action to reduce greenhouse gas emissions. The

second large group should state a case for waiting

until there is scientific certainty. Students should use

the library to research current information about

global warming and then consider and debate the

question.

Discussion

When is evidence sufficient to have confidence in the

data set and take action based on it? When is a sample

of a subset enough to have accurate results (as in taking

a survey)? What are other issues that could impact the

decision of whether or not to act (for example, might it

be good to reduce use of fossil fuels for other reasons)?

88

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES


Back to the Future

Objectives

Students will be able to: 1) describe the changes that

have taken place in their regional environment during

their lifetime; 2) explain how past choices have impacted

their current environment and how their choices now will

impact the future.

Method

Students will compare aerial photos of their area from the

past with current photos, noting differences and then

conducting ground truth investigations to determine what

happened. Finally, students will use the information they

gather about past changes to make predictions about the

future.

Background

Encouraging today’s students to understand and take

responsibility for environmental changes may be the best

hope we have for preserving Earth’s natural resources

into the future. In every region, choices made by past

generations impact the environment their children live in.

This activity offers students the opportunity to examine

the impacts that past choices have had on their surroundings

and to project the kinds of impacts their own choices

will have on their children’s environment.

Through this activity, students will become aware of

their watershed, nearby park lands and natural areas, the

impacts of recent development, resulting changes in

human, animal and plant qualities of life, economic,

civic, political, and historical issues that impact development,

and the whole range of land use questions that

exist for every region.

Age

Grades 4 -12, customized for each level

Subjects

Geography, Science, Social Studies, Math

Duration

Several one hour class periods, plus outside work

by students

Skills

analysis, considering responsible action,

determining trends, image interpretation,

prediction

Key Vocabulary

data, ground truth, land use, prediction,

remote sensing, vegetation, watershed

Materials

Regional maps and aerial or satellite images from

10 to 15 years ago and recent photos (this is an ideal

interval because it approximates the lifetime of the

students so far, but if these are not available, use whatever

interval you can get. See the appendices for information

on obtaining RS images), graph paper, paper and pens,

straight edge, access to a local research library and other

sources of local statistical data such as the Public Service

Company or the County Zoning Authority.

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Back to the Future (continued)

Procedure

1. Give small groups of students regional aerial or

satellite images from 10-15 years ago and today.

Have them study and compare the photos, looking for

differences between them. The photos may not have

been taken at approximately the same time of year,

and students should check for the existence of any

extraordinary circumstances, such as seasonal

variations or a major drought, that could account for

differences.

2. Students should make two identical grids [offer

guidance on grid size here] and lay them over the two

images. Let them study the images to locate 10 sites

which are the same and 10 sites which are different in

the corresponding grid boxes on the old and new

photos. Students should make predictions about what

the differences indicate. With the aid of a local map,

students can locate the actual areas which correspond

to the grid boxes in which the differences occur. Then

they should plan and embark on a “ground truth”

investigation. On the ground truth investigation, the

students should record their observations of crops,

trees, vegetation, developed areas, etc., and compare

these observations with their hypotheses about the

differences they observed between the two images.

Alternate Procedure

1. If only a recent image is available, students should

learn as much as they can from the current image and

using this information, make predictions about the

future. Their predictions can use the grid overlay as a

method of creating a map of the future. (Pretend you

are a remote sensing scientist in orbit about Earth,

and have the assignment of projecting the future

trends of the area covered by the aerial photo in this

activity.)

2. Tie the activity into current issues, e.g.. planned

highways, dams, housing projects, greenbelts. Give

4-5 groups the same assignment, compare their

results and discuss the decisions they made.

Extension

1. Based on the results of their study, have your

students make a representation of what they project

the region will look like 10-15 years in the future. To

make their predictions more accurate and meaningful,

they should collect statistical information such as

lists of all the towns and cities in the region and their

populations 10-15 years ago and today. In addition,

they should collect data on current rates of population

growth, numbers of dirt roads which have been

paved, changes in total traffic miles driven, and

similar information that would assist the process of

preparing a prediction of what the area will look like

in 15 years.

2. In preparing this prediction, students should determine

and extend forward any discernible trends that

have formed over the past 10-15 years, using relevant

information on rates of change that they discover.

Students need not attempt to provide an unbiased

assessment of what they would like to see happen or

what they fear could happen, etc. After making and

sketching their prediction, students can then go on to

sketch pictures of alternative futures, including what

they would consider to be the ideal future and a

worst case scenario. Have your students discuss what

they can do to turn around negative aspects and

preserve what they would like to see protected.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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Map Your Watershed

Objectives

Students will be able to: 1) identify, describe and outline

watersheds on a topographic map; 2) determine the

direction of water flow; 3) discuss and explain the size

and importance of watersheds.

Method

The students will learn to identify watersheds on

topographic maps by learning how to interpret contour

lines and distinguish adjacent watersheds by the ridge

line between them.

Background

A watershed is the whole region from which a river

receives its supply of water. Watersheds may be identified

on topographic maps by the contour lines which

represent different elevations, or heights, of the land

surface. Because water flows downhill, adjacent watersheds

are separated by areas of higher ground. This high

ground is called a ridge line, and is represented by the

contour line of highest elevation between two watercourses

on a topographic map. The area of a watershed

can be outlined by tracing the ridge line or contour line

of highest elevation enclosing it. Contour lines represent

surface relief by connecting the points having the same

elevations. Contour lines represent a difference of 40 feet

in elevation on a 7.5 minute series map from the United

States Geological Survey (USGS), but may represent

different elevations on maps of different scales, and this

“Contour Interval” is printed on each topographic map.

A single contour line always forms a closed figure.

Contour lines on a map never intersect because each

point on the surface has only one elevation. Closely

spaced contour lines represent steep land because the

elevation changes rapidly in a short horizontal distance.

Age

Grades 7 - 12

Subjects

Geography, Geology, Math

Duration

One or two class periods, depending

on the detail

Skills

map interpretation

Key Vocabulary

contour line, gradient, ridge line, topographic

map, topography, watercourse, watershed

Widely spaced contour lines represent flatter terrain in

which elevation changes little across long horizontal

distances. The ratio of change in elevation to change in

horizontal distance is called the gradient or slope of the

land.

Materials

Laminated 7.5 topographic maps of your city and the

local watershed for each pair or small group of students,

grease pencils. Topographic maps may be obtained from

libraries, map stores, some book stores or wilderness

outfitters, and the United States Geological Survey.

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Map Your Watershed (continued)

Procedure

1. Introduce the topographic maps as the two-dimensional

representation of the physical features of an

area. Some of your students may be familiar with

“Topo Maps”. Ask them to help explain them to the

class. Ask the groups to locate your town and a local

stream or river on their map.

2. With reference to the topographic map key, ask your

students to locate contour lines on their maps and to

determine the elevation difference which they

represent. Introduce the concept that contour lines

each lie along a particular elevation. Discuss what

kinds of land forms widely spaced or closely spaced

contour lines represent. Locate the contour lines

representing the lowest and highest elevations on the

topographic map.

3. Because water flows downhill, it is possible to

determine which land area drains into the stream or

river under study. Locate the contour line of highest

elevation that encloses the stream or river, and mark

it with a grease pencil. This indicates a ridge line; on

one side of the ridge, water will flow into your stream

or river, and on the other side of the ridge it will flow

into the neighboring watershed.

4. Have your students trace where the water they use

(like drinking and washing water) comes from and

where it goes after they are finished with it. Was their

water used by someone else upstream? Will it be used

by someone else further downstream? How is the

water quality affected by this use and reuse?

Discussion

Organize a discussion with your students by asking the

following questions:

• How do the contour lines appear on this map and

what do they show?

• Do the contours make a V-shape up or down

stream? In what direction does the stream or river

flow? How can they tell?

• About how many feet does the stream or river fall

as it crosses the area on the map?

• What is the average width of the stream or river you

are examining and what is the approximate area of

your watershed?

• What land forms do crowded contour lines represent

and what land forms do widely spaced contour

lines represent?

Extension

1. Use the Plane-Table and T-Stick mapping techniques

mentioned in the extension of “Sandboxes and

Satellites” activity to make a contour map of the

school grounds or a local park. This would be best

carried out in an area with considerable topographic

variation.

2. Using the topographic map, ask the students to

determine the approximate length and area of land

which would be flooded if a dam was built on the

stream over the river near a town, what would be its

length, and what would be the approximate area of

the lake behind the dam?

Evaluation

1. Locate and describe the following features on a

topographic map: watercourse, contour line, and

ridge line.

2. Trace the ridge line between two adjacent watersheds

on a topographic map.

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Land Cover Mapping

Objectives

Students will be able to: l) recognize and explain the

differences between satellite images and topographic

maps; 2) identify different land cover types on satellite

images and relate them to the corresponding areas on the

topographic maps; 3) explain the relationship between

cover types, water flow, and water quality.

Method

Students will use remotely sensed images and topographic

maps to classify land cover types in their

watershed. A field trip to specific sites will allow the

students to “ground truth” cover types found on the

remotely sensed images and extrapolate that information

to other sites not visited. If possible, a second field trip

will allow students to test their interpretive skills with

reality, by visiting new sites for which they were asked

to determine the land cover solely from a remotely

sensed image.

Background

Land cover, in remote sensing, refers to the primary

reflective or emitting surface detected by sensors. Land

cover differs from forest or vegetative cover in that it is

all inclusive and includes everything detected by the

sensors: Trees, fields, houses, lawns, lakes, roads and

parking lots, etc. Land cover significantly influences

water flow and water quality. Because vegetation

intercepts precipitation with its many surfaces, it slows

and decreases runoff (the flow of water across the land

surface). Runoff is faster and greater on bare ground or

paved surfaces. Vegetation cover permits more infiltration,

or soaking of precipitation into the ground, because

root channels keep the soil loose and decaying organic

material, or humus, acts as a sponge. Impermeable

paved surfaces do not allow infiltration for recharge of

Age

Grades 7 - 12

Subjects

Biology, Geography, Geology,

Science, Social Studies

Duration

One or two class period

and one or two field trips.

Skills

image interpretation, mapping,

plant identification, scale

Key Vocabulary

false-color, infiltration, riparian zone, runoff,

scale, sediment, turbidity, spectral reflectance

the soil moisture and groundwater reserves.

Because land cover influences water flow across a

watershed, it directly impacts water quality in the

watercourse. If vegetation is removed, precipitation hits

the soil surface more energetically and runs off more

quickly, carrying with it greater amounts of soil and

plant nutrients. This results in increased erosion,

watercourse turbidity, and decreased water quality.

Eventually, the suspended soil particles settle to the

bottom of the watercourse as sediment, perhaps suffocating

riverbed organisms or filling in reservoirs behind

dams. On the other hand, sediments may settle during

receding seasonal floods, renewing the fertility of

riverside agricultural fields. Runoff may enter a

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Land Cover Mapping (continued)

watercourse at a temperature quite different than the

water already there. A temperature change may benefit

some organisms living in the water while making it less

suitable for others. For example, trout require cold

water, but catfish prefer warmer water. Runoff may

bring bacteria, pesticides, or toxic chemicals from the

land into watercourses, thus decreasing water quality.

Mining, road construction, housing developments,

industrial expansion, and the conversion of forests to

cropland all decrease the amount of vegetative land

cover. Reforestation, mine reclamation, residential

landscaping laws, soil conservation ordinances, the

creation of parklands, and the cultivation of perennial

instead of annual crops all increase vegetative land

cover. Conversion of land cover in the riparian zone

bordering a watercourse can directly affect water quality.

The removal of trees shading a watercourse will increase

water temperature while the planting of trees will

decrease water temperature, wind speed, and evaporation

in the riparian zone.

The purpose of this activity is to teach students how

information gained from a small sample of sites can be

used to interpret remotely sensed images and to make

educated guesses as to the extent of similar types of land

cover within their watershed. Maps are generalizations

of reality, often containing numerical or alphabetical

information as well as selected and adjusted graphic

detail.

Within limits, different objects, such as areas of different

land cover, can be distinguished on remotely sensed

images because they each have a unique spectral

signature. That is, each type of vegetation or material

covering the land reflects or emits a unique radiation

pattern that is sensed and recorded. To a certain degree,

then, it is possible to differentiate between different

types of land cover. Thus corn fields, pine forests, open

water and concrete buildings may all appear differently

on remotely sensed images.

There are limitations to what can be interpreted from

any remotely sensed image. While it will almost always

be possible to tell a paved parking lot from an agricultural

field, it may not be possible to tell a gravel or dirt

parking lot from fallow (unplanted) agricultural field, to

determine whether a field contains corn, barley, wheat

or rye, or to distinguish a marsh from a rice field

without more information than is available in one

satellite photo.

Materials

Topographic maps and aerial or satellite images of your

watershed that have been laminated or have acetate

covers; grease pencils or tracing paper, pencils and

rulers.

Procedure

1. Ask your students to locate their watershed on both

their map and satellite image.

2. Introduce the concept of spectral reflectance. Each

type of vegetation or material covering the land

reflects or emits a unique electromagnetic signature

that is recorded by the satellite sensor and appears as

a uniquely colored entity on the satellite image.

With a grease pencil on the laminated satellite

image, or with a pencil on tracing paper, outline ten

areas in your watershed that appear distinctly

different on the image, indicating different land

covers.

3. On the basis of their knowledge of the area, your

students should record what might be the ground

cover on each of several areas which are close

enough to the school for a field trip to test their

accuracy.

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Land Cover Mapping (continued)

4. Take your students on a field trip to a few of the

representative sites. Bring along the maps, images,

and outlines as you visit the various parts of the

watershed. Your students should record the cover in

each of the areas that they outlined. Have them

compare their predictions of land cover to what is

actually there.

5. Back in the classroom, have your students reconsider

the accuracy of their predictions on the basis of the

evidence from their ground truthing.

Discussion

Organize a discussion with your students by asking the

following questions:

• What vegetation symbols appear on the map and

how do they compare with the remotely sensed

images?

• Which is older, the map or the satellite image?

What indicates that one is older than the other,

other than the dates printed on the map and image?

• How does the appearance of towns and cities differ

between the map and satellite image?

• If the contour lines on the map were erased, what

clues would you have about the location of high

land? The remotely sensed image has no contour

lines—can the students find clues as to the outline

of the watershed?

• What indicates the deeper and more fertile soils?

Are they on the low or high land?

• How would your students describe the texture of

the different different classes of cover that you see

on the satellite image?

• What percentage of the local watershed is covered

by forest, by grasslands, by agriculture, by human

settlements, etc.?

Extension

Have your students work in groups to make additional

land cover maps using satellite images. Compare the

percentages of land cover types in the local watershed

with those in a similar ecosystem in another country.

Compare the percentages of land cover types in the local

watershed with those in a watershed in a different

ecosystem. Discuss how human activities may account

for the differences in amounts of various land covers,

and any indications of differing water quality.

Evaluation

1. Describe several ways in which satellite images are

different from topographic maps.

2. Locate and name all the land cover types you can

find on the satellite image.

3. Locate and name all the land cover types you can

find on the topographic map.

4. Explain how different types of land cover affect

runoff and infiltration.

5. Describe several human activities that change land

cover and thereby decrease water quality. Explain

the impacts.

6. Suggest some possible changes in land cover that

humans could make in the watershed to increase

water quality.

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A Changing Watershed

Objectives

Students will be able to: 1) relate changes that have

occurred to the local watershed to local history and

development; 2) describe how these changes have had

positive or negative impacts on water quality in the

watershed.

Method

Students will examine two satellite images of their local

watershed taken at different points in time and use this

data to learn about changes in the watershed, particularly

in land cover. As an alternative, or if you are short of

images from different times, students should interview

family, neighbors and “old-timers” and use old and

recent photos to develop a “then and now” theme.

Background

The purpose of this activity is to increase your students’

awareness of change as both ecological and social

phenomena of a watershed. Changes, particularly land

cover changes, occur in watersheds through time as a

result of both natural forces and human actions, and these

changes, in turn, affect water quality in steams and

rivers. This activity closely parallels the activity, Back to

the Future, but has its main emphasis on features which

directly impact water quality in your watershed. Ask the

students to look at positive as well as negative impacts. It

is easy to forget or overlook positive measures which

have been taken to protect or restore water quality in

many areas. Since public awareness and action on water

quality issues began in the late ’60s, there will have been

many local success stories about rivers being “brought

back to life” through the actions of aware and concerned

citizens, often students such as yours.

Age

Grades 7 - 12

Subjects

Social Studies, Language Arts, Geography, Science

Duration

Two class periods

Skills

image interpretation, mapping

Key Vocabulary

Land cover

Since 1972, Landsat has been remotely sensing nearly

the entire earth every 18 days. Sometimes clouds obstruct

the view of the sensors; this happens more often in some

regions than others. Despite the vagaries of weather, at

least two clear Landsat images exist for most locations.

Two or more satellite images of an area form a time

series that can be used to assess changes in the watershed,

particularly changes in

land cover.

On images from temperate zones, changes in the

appearance of vegetation, or the extent of snow cover,

will help distinguish seasons. The lush growth of summer

will contrast with the barrenness of winter. Evergreen

trees that are difficult to distinguish in mixed forests will

contrast sharply with the leafless deciduous trees in

winter images. In summer scenes, the same crop will

often have the same texture even if in a different stage of

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A Changing Watershed (continued)

growth; this assists in determining if a field has been

planted with the same or different crops in successive

years.

On images from other climate zones, the lushness of

vegetation may indicate wet or dry seasons. Rivers or

other water bodies may increase their size in flood, and

may decrease in size seasonally or in unusual droughts.

Even without standing crops, cultivated land may often

be distinguished from natural vegetation by the regular

pattern of the fields.

At the edges of cities and towns, or along roads, rivers,

or beaches, the expansion of residential or industrial

areas may be evident. At the boundaries between land

cover types, conversion from one type to another may be

discerned. In addition to incremental changes like these,

there may be catastrophic changes in vegetative cover

caused by forest clear cutting, windstorms, fires,

landslides, or volcanic eruptions.

Materials

At least two satellite images of the local watershed from

different points in time (as used in the activity Back to

the Future), topographic maps. Have the satellite images

laminated or protected with clear acetate.

Procedure

1. Ask your students to study the pairs of images,

carefully noting differences in land cover (as

described in the previous activity) which would have

direct impacts on the watershed. These might include

new tracts of housing, shopping centers and roads, or

areas newly designated as parks or green-ways. List

and describe the differences found. Locate the areas

of change on a topographic map and suggest why

these land cover changes may have occurred, given

what is known about these areas.

2. Can your students detect any differences in the width,

color, or flow path of the stream or river? Ask them

to explain these changes in the river in relation to the

land cover changes found.

3. Determine the size of the area converted from one

land cover to another over the time period represented

by the satellite images. Calculations may include the

following areas: total area converted from one land

cover to another; expansion or contraction of human

settlements, natural vegetation, or agriculture;

conversion of one agricultural land cover to another;

conversion attributable to windstorms, fire, landslides,

or volcanic eruption. Present these calculations

in the form of a graph. Predict the land cover in the

watershed ten or twenty years from now if the trends

in the time interval represented by the satellite images

continue.

4. Propose ways in which information about local cover

changes that appear in satellite images could be used

to plan desired changes and to monitor undesired

changes in the watershed or water quality in the

future.

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A Changing Watershed (continued)

Discussion

Organize a discussion with your students by asking the

following questions:

• In which season of the year were the images taken?

Is it possible to tell this from the image alone?

Would it be possible to tell which year (perhaps a

specific event is occurring)? What day of the

week?

• What indications are there on the images that some

areas once had a different land cover than they do

now? For instance, what indications are there that

some areas were once forested, or were once

beaches, and are not now?

• What is the average width of the stream or river at

the same point on the two satellite images? What

explains the similar or different average width?

• What might be some reasons for the location of the

towns? In what ways are the towns and cities

growing or shrinking? How is the area covered by

the towns and cities affecting the river?

• What forms of land cover change are occurring

most rapidly, and which are occurring most slowly

in the watershed? What are some explanations for

these different rates of land cover conversion?

• What are the advantages and disadvantages of these

land cover changes for the people living in the

watershed?

• What are the impacts of these land cover changes

on the quality of water in the stream or river?

Extension

Compare the rates of land cover conversion in the

local watershed to their counterparts for the state or

the country. This data can be found in yearbooks,

almanacs, and government publications. Explain how

these state or national land cover conversion rates

could be determined or verified using satellite

images. What are the implications of the land cover

changes over larger areas for the water quality of

streams and rivers in the state and the county?

Propose possible explanations for the similarities and

differences found in the land cover conversion rates

in the local watershed, the state, and the country.

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Your Watershed’s Story

Objectives

Students will be able to: 1) devise and carry out interviews

within the community; 2) name several natural and

human activities that have changed the local watershed in

living history; 3) describe the interaction between the

river, its quality and the lives of people in the watershed.

Method

Students will design a questionnaire, interview local

people, and compile the oral histories collected to

establish the recent history of a river and its watershed.

Students must have a firm grasp of the meaning of

watershed in order to be able to interview other people.

Background

Anthropologists and ethnographers use interviewing as a

research technique to collect oral histories: accounts of

places and events that are not written, but passed on from

one generation to the next verbally. Oral histories are

usually the re-telling of the personal, daily lives of

ordinary people, in their own words. Collecting oral

histories provides students with an exciting way to forge

links with people of various ages and to accumulate the

wisdom of experience. The purpose of this activity is for

students to gain an appreciation for the rich information

contained in oral histories, and the complex ways in

which watershed changes affect people’s lives. Learners

more easily establish the connections between events and

the context in which they occur because interviewing

makes history more personal.

Materials

Writing materials, tape recorders, blank tapes, aerial or

satellite images, topographic maps or watershed model of

the local watershed.

Age

Grades 7 - 12

Subjects

Social Studies, Sociology, Anthropology,

Science, Language Arts

Duration

At least two class periods plus time outside of

class for conducting interviews

Skills

compiling information, designing

questionnaires, interviewing

Key Vocabulary

anthropology, ethnography, meander, oral

history, political boundary, raw materials, value

judgement

Procedure

1. To prepare to interview older members of the

community to find out what various parts of the

watershed were like in years gone by, divide the

learners into small groups to generate questions to be

asked during interviews. Compile all questions

suggested. As a large group, decide which questions

to place on a questionnaire to insure that a minimum

standard of similar information is sought with each

interview. Interview questions might include:

• How long have you lived in the area?

• What were the river and the surrounding

watershed like when you were my age?

• What are the different uses of the river that you

have witnessed?

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Your Watershed’s Story (continued)

• How has the land in the watershed been used

during the years that you have lived here?

• What do you think has caused changes in the river

or watershed?

• How do you feel about the changes that you have

witnessed?

• What do you think this watershed and river will be

like in the next ten to twenty years?

2. Have the students rehearse their interviews by roleplay

with fellow students prior to the actual interviews

with community members. Practice drawing

out specific examples when people make general

statements.

3. Each student or group should contact older relatives,

historical society members, or senior citizens to

arrange interviews. The students should inform each

interviewee of the purpose of the interview, how long

it will last, how the interview results will be used, and

what the questions

might be.

4. At the beginning of the interview, students should ask

permission to take notes or tape record the interview

conversation, and abide by the wishes of the

interviewee concerning making records of the

conversation.

5. Ask each of the questions on the questionnaire.

Encourage specific examples whenever the person

interviewed makes general statements. Ask the person

to indicate on the satellite image, map or watershed

model, the places in the watershed that they describe.

Note the natural and human forces of change to which

they attribute changes in the watershed. Listen for

value judgements that they attach to the changes that

they have witnessed. Enquire about the changes they

think will happen in the future and their attitudes

about these changes.

6. Each student should prepare a written report of the

interview findings in the form of a feature article for

a newspaper, or a chapter in a biography. Ask

learners to illustrate their report with pictures of the

watershed as it appeared in the past, or with a cover

map of the watershed in the past.

7. All of the interview reports should be compiled into a

booklet. Find old photographs to complement the

text. Perhaps the persons interviewed, the historical

society, or the local newspaper have photos that they

would allow to be used as

illustrations.

Discussion

Organize a discussion with your students by asking the

following questions:

• How has the river or stream been affected by the

human use of raw materials available in the

watershed?

• Does any part of the river correspond to a political

boundary? If so, how might this give rise to

difficulties?

• Why are some areas of river meanders built on and

others are not?

• What reduces or increases a river’s usefulness for

transport?

• What are the major economic uses of the river?

• How would the satellite image or map have looked

fifty or one hundred years ago?

• How may the satellite image, map, or watershed

model appear ten to twenty years from now?

• How might different attitudes toward change affect

how the watershed appears then?

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Your Watershed’s Story (continued)

Extensions

1. A small group of learners may prepare questions and

arrange for three or four interviewees to gather for a

television talk show type program titled “Your

Changing Watershed” before a live audience of the

whole group of learners. This program may be

videotaped for presentation later to younger learners

or to a ‘family night’ audience.

2. Write a story as if the local stream or river could talk.

Include the changes that the river has noticed in the

past 100 years, the river’s opinion of its water quality,

and its opinion of the future of the watershed. What is

the river’s reaction when it finds out that Landsat

records its appearance on a satellite image every

eighteen days, and that such images can be used for

planning or monitoring changes in watersheds and

water quality? If the river could speak for one hour,

who would it like to talk to, and what would it say?

What questions would the river like to ask? Illustrate

the story with drawings, paintings, photos, or

collages.

3. Make a timeline of the river’s history and the use of

the land surrounding it. Illustrate the timeline with

photos or drawings of how the various parts of the

watershed looked in the past. Display this timeline in

the school, a mall, library, city hall, or other place

where people in the community may learn from it.

Evaluation

1. Name several natural forces and several human

activities that have changed the watershed in living

memory.

2. Describe some of the most important ways in which the

river has historically affected the lives of people in the

watershed.

3. Describe the relationship between changes in the

watershed and river water quality, and people’s

attitudes toward those changes.

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Make a Watershed Model

Objectives

Students will be able to: 1) describe the topography of

the watershed as a three-dimensional model; 2) locate

corresponding features on topographic maps and a threedimensional

model; 3) describe the interactions between

the watershed and human activities.

Method

A three-dimensional watershed model will be created and

used to trace the flow of water across the land and down

a stream or river. Students will create the model from a

two-dimensional topographic map. They will use the

model to trace the path that a water droplet takes across

the watershed and into the watercourse, and will describe

the relationship between the physical features of the

watershed and the location of human activities.

Background

Students are often familiar with only a small portion of

the watersheds within which they live. Building a

watershed model and tracing the flow of water in the

watershed can assist them in understanding the relationship

between the different features of the watershed, and

the interdependence of the human activities in the

watershed. This watershed model can be used as an

important instructional aid for many activities about the

watershed.

Many human activities are influenced by the flow of

water across different land forms in a watershed. People

locate their farms and towns along watercourses to have

a water supply for their homes, their crops and animals,

and their industries. People live near watercourses to

have transportation for the things they need or produce.

People have observed the hazards of flood plains and

employed the relative safety of natural levees for their

building activities. Where rivers impede transportation,

Age

Grades 7 - 12

Subjects

Geology, Geography,

Social Studies, Language Arts, Science

Duration

3-4 hours

Skills

physical modelling

Key Vocabulary

floodplain, levee, watercourse

bridges have been built. Bridges are often placed where

the watercourse is narrow, where the banks on either side

are the same height, and where the water is not too swift.

Trains cannot travel on steep slopes like cars, trucks, and

buses, so railroads are found in flatter areas of the

watershed, while roads may exist in even the steepest

areas. Airports require large flat areas for their runways

and even larger areas without tall obstructions, so they

are often located on the ridge lines or in wide valleys of

the watershed.

Sometimes humans change the shape of a watershed or

the flow of water across it for their own needs. Farm

fields may be terraced, made to look like stairs with

retaining walls, to slow the flow of water downhill. Dams

may be built across watercourses to provide water deep

enough for navigation, to generate electricity, or to create

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Make a Watershed Model (continued)

drinking water reservoirs. Valleys may be filled or hills

cut away for the building of railroads or highways.

Materials

Topographic map of your watershed, tracing paper,

tempera paints, paint brushes, cutting knife or saw,

plaster of Paris or paper maché, plasticene or other

waterproofing, and corrugated cardboard, plywood or

other media from which to cut layers representing each

of the contour intervals in your watershed.

Procedure

1. Use one piece of your layering material as a base.

Trace the lowest elevation contour on tracing paper

and then cut away all of the area below this contour

elevation. Use this as a pattern to cut this contour

interval from your layering material. Attach the layer

at the proper position to the base. Repeat this tracing,

layer cutting, and layer attaching process for each of

the successively higher elevation contours. The result

is a three-dimensional model of your watershed.

Plaster of Paris or paper maché can be used to smooth

the edges of the various layers. Use tempera paints to

indicate the watercourses, beaches, rock outcrops,

forests, buildings, roads, towns, or other features in

your watershed.

2. Place the model in a sink or outdoors where water

running off of it will not cause any problems. Place

an eye dropper full or a spoonful of water on the

model and watch where it flows. Try placing water at

several different points on the model simultaneously

to determine how the water flows during a rainstorm

or spring snow melt.

Discussion

Organize a discussion with your students by asking the

following questions:

• Do the roads or railroads appear to respond to relief

— meaning, do they follow the grade up and down

or simply plow through without responding to the

existing terrain? Why are the railroad cuttings,

tunnels, or bridges where they are?

• Which landforms correspond to closely spaced

contour lines and which ones correspond to widely

spaced contour lines? Which river in the watershed

has the steepest-sided valley?

• What are some possible reasons for the location of

particular facilities, such as sewage treatment

plants, an airport, or industrial plants, within the

watershed? What path would you suggest for a

walking path, a biking path, a motor vehicle path,

and a flight path across the watershed?

• Where would you recommend building new houses

or industry in the watershed? At which locations in

the watershed would you ban further building?

Extensions

1. Divide the learners into groups to make more than

one model. Make a model of the watershed as it was

ten years or one-hundred years ago, or as it was

before the last Ice Age. What sorts of changes occur

at the different time scales? How have human

activities changed the shape of the watershed?

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Make a Watershed Model (continued)

2. If the local stream or river is a tributary of another

watercourse, make a model of the larger watershed.

What are the similarities and differences in the two

different scale watersheds?

3. Make a model of a watershed in another part of the

state, country, or world. Compare it with the local

watershed. What features might be common to all

watersheds? How do the relationships between the

physical features and the humans in the two watersheds

compare?

Evaluation

1. Locate several natural physical features and several

human-made features on the topographic map, and

locate their corresponding position on the watershed

model.

2. Describe a few important ways in which the physical

features of a watershed influence the location of

human activities.

3. Describe ways in which human activities change the

shape of the watershed, and consequently, the path

along which water will flow.

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River Walk

Objectives

Students will be able to: 1) describe how local land uses

influence river water quality; 2) use both visual and

olfactory stimuli as indicators of water quality; 3) pose

pertinent questions concerning aspects of the river that

require action or further investigation.

Method

Through a field trip along a local water course students

will conduct a visual survey to discover information

about local land use and water quality. They will

document their findings with mapping and compilation

of a river profile and use this initial reconnaissance to

raise questions about local land use or river water quality

that require investigation.

Background

Many factors can affect the quality of a river system. The

conditions of a river can fluctuate. What is high quality

in one area may be low quality in another, while some

factors, such as pollutants, are a hazard to any watershed.

Cold water that is good for trout may be fatal for catfish

or bass, and vice versa, but discharges of industrial or

agricultural wastes will be detrimental for all life in the

water. Water quality monitoring can begin with one’s

visual and olfactory senses (Refer to the activity:

Learning to Look, Looking to See); it does not require

sophisticated equipment. Common constituents and

pollutants in water have characteristic appearances and

smells that can be observed for an initial determination of

water quality. Field observations increase one’s ability to

conceptualize links between land use and water quality.

Age

Grades 7 - 12

Subjects

Biology, Geography, Social Studies,

Language Arts, Science, Math

Duration

Three hour field trip

Skills

field observations, flow & current, mapping

Key Vocabulary

algae, erosion, olfactory, point source, runoff,

sedimentation, tannin

Materials

Clip board, pencils, data sheets, local map, aerial or

satellite images and the watershed and land cover maps

that were created earlier.

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River Walk (continued)

Procedure

1. Ideally, small groups of students should walk and

survey designated stream or river segments appearing

on the watershed map which they made earlier. If

watershed maps were not made, local topographic

maps encompassing the stream or river can be used,

and are helpful in any case for showing roads and

other reference points. Accessibility and safety are

two criteria for designating these segments. Each

segment should be bound by conspicuous reference

points: bridges, monuments, roads, or distinctive

natural features. An appropriate length for each

segment is site-specific, but l km segments are

suggested. Familiarize everyone with safety procedures

before beginning the walk.

2. Stream or river segments may be coded or labeled to

abbreviate the river’s name and to indicate the

relative position of the segment along the stream or

river. For example, the segment at the mouth of the

Arkansas River, USA, might be labeled AR1, the next

segment upstream AR2, etc.

3. During their walk each group completes a data sheet.

The group also records its observations on a stream

map. As each group walks their stream segment,

bordering land uses should be noted: urban, industrial,

residential, agricultural, woodlands, swamp, and

others. Tributaries and point sources of pollutants,

such as discharge pipes, open sewers, and ditches

should also be shown on the map as well as the

direction of flow. Your students may decide to use

topographic symbols or symbols of their own

choosing to denote land uses and human-made

structures.

4. Each student should write a personal narrative

account of the walk. Encourage richness of detail

about uses bordering the watercourse, colors and

odors, human usage of the river, suspected pollution

sources, and the students’ perceptions of and reflections

on being at the river. Unique or significant

features could be referenced to the small group’s

map.

5. Assemble the maps according to their relative

positions along the stream. Exchange data sheets

among all small groups. Look for similarities,

differences, and patterns among the observed

characteristics of the segments.

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River Walk (continued)

Discussion

Organize a discussion with your students by asking the

following questions:

• What type of water appearance was recorded most

often and what does this indicate about the water

quality of the stream or river? What might be the

source of material creating this appearance? How

does the appearance of the water change from

upstream to downstream?

• Which human uses of the river were found with

which land covers? If two land cover types were

reversed in their order along the stream or river,

what changes might this make in the appearance of

the river?

• What kinds of habitats were observed to be most

extensive along the river or stream? If one of the

most extensive habitats along the river or stream

was eliminated, what effect might it have on

wildlife? What effect might it have on human uses

of the river?

• What is the total number of barriers found in the

segments investigated? Were the majority of the

barriers naturally occurring or human-made? What

are some reasons humans have created barriers?

• What do the odors noticed along the river indicate

about the water quality? How could the weather on

the day of the walk and the day before the walk

have influenced the water quality?

• As you exchanged narratives with a partner, which

river characteristics did you both mention, and

which characteristics did just one of you mention?

Why might your perceptions vary? What implications

do differing perceptions among people in the

watershed have for choosing land uses, and for

solutions to water quality problems?

Extension

1. Bring your students atop a high place from which the

whole segment of the river walk is visible. On the

watershed map or land cover map, sketch in the

boundaries of landform or land use subdivisions that

are apparent from the high vantage point. Write a

description of the area to accompany the map. Try to

place the river segment in context in the watershed

and between other segments. Begin by stating the

location of the segment and its length and breadth in

miles. If fairly uniform, give the general altitude of

the area. Describe distinguishing landforms, including

waterfronts, drainage pattern, vegetation types,

minerals, and cultural features such as communication

or transport systems and their responses to relief

and drainage, land use and land cover, occupations in

the area and so on. Distinguish between what is

actually seen and what is surmised. The written

descriptions of the river segments and their surroundings,

along with corresponding sketch maps, could be

compiled into a travelogue booklet.

Evaluation

1. Describe the relationship between visual and

olfactory indicators and water quality.

2. Pose several questions about the river’s water quality

that require further investigation.

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Regulatory Agencies on the River

Objectives

Students will be able to: 1) list and identify functions and

jurisdiction of at least three governmental agencies

charged with safeguarding water quality; 2) explain the

concern over water quality; 3) explain how citizens can

have a role in the action of governmental agencies.

Method

Learners will identify existing government agencies

charged with safeguarding water quality, their geographic

jurisdiction, and their subjects of concern, such

as water quality laws, information, testing, and enforcement.

They will explain the role of citizen action in these

agencies, and locate the names, telephone numbers, and

addresses that citizens may use to contact the agencies.

Background

Regulatory agencies at all levels of government have

certain responsibilities and authority to protect public

safety and water quality on rivers and other bodies of

water. Regulations are principles, rules, or laws to govern

behavior. Water resource regulations have been created

and are enforced because some people are inconsiderate

of others, some aspects of river and waterways (such as

floods) are unpredictable, and some services (such as

water treatment) are more efficient when provided on a

larger scale. The purpose of this activity is to increase

learners’ understanding of regulatory agencies charged

with water resources management, how citizens have

input into these agencies, and to increase skills in

locating sources of political, social, economic, and legal

information about regulatory agencies and citizens’

organizations.

Human behavior may be changed by means other than

regulation. Education can alert people to the unknown

Age

Grades 7-12

Subjects

Social Studies, Science

Duration

Four class periods, plus independent research

Skills

research

Key Vocabulary

jurisdiction, regulation

hazards of building on flood plains. Economic incentives

can encourage industries to reuse their by-products rather

than to discharge effluents into a river. Peer pressure or

philosophical reasoning can persuade people to be more

considerate when fishing, or to avoid littering in and near

the river.

Agencies at all levels of government in the United States

have been charged with water resources management.

They include, but are not limited to the following:

• International agencies like the International Joint

Commission which resolves mutual border problems

between Canada and the United States.

• Federal agencies such as the Soil Conservation

Service (SCS) which works with farmers to try to

minimize erosion, or the Environmental Protection

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Regulatory Agencies on the River (continued)

Agency (EPA) which sets water quality standards.

Most federal agencies with water concerns are

under the jurisdiction of the U.S. Department of the

Interior.

• State agencies such as a Department of Natural

Resources are charged with protection and management

of water resources along with forests, wildlife,

minerals, etc.

• County agencies like the Public Health Department

monitor the safety of drinking water and of bathing

beaches.

• Local agencies like the Department of Water

Supply and the Department of Wastewater Management

provide services to individual clients in the

city

or district.

• Private water quality testing firms are often an

excellent source of information on local water

quality issues, even though they are not regulatory

agencies themselves.

Materials

List of regulatory agencies at different levels of government

which have primary water resource responsibilities,

phone book, writing materials, envelopes, pens, postage,

access to a telephone.

Procedure

1. Each small group of students should choose one

agency to investigate. Tell them that they will be

responsible for informing the rest of the class about

their particular choice. They will be the experts on

their agency. Through library research, phone calls,

letters and even visits to the respective offices,

students should determine the laws, standards,

enforcement, and penalties for which their particular

water resources agency is responsible. Obtain the

address and phone number of the agency’s nearest

office, and the name of someone to contact in that

agency concerning its water resources work.

2. After determining which agencies would find the data

useful or which would address the kinds of concerns

identified during the river walk, make appointments

with agency staff members to present the group’s

observations, discuss the water quality problems

identified, and possible solutions

generated.

3. Each group should report back to the class on their

agency and the results should be posted in graphic

form so that the students can see how each agency

interacts with or compliments the others.

Discussion

Organize a discussion with your students by asking the

following questions:

• What are the names and responsibilities of the

regional, federal, state, county, and local agencies

which have primary water resource responsibilities

in the local area?

• Why are regulations associated with water resources

necessary to protect public health and

safety?

• What measures other than regulations may be used

to maintain the health and safety of water resources?

• What are some difficulties encountered by water

resources agency staff in creating and enforcing

regulations? How might these difficulties be

overcome?

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Regulatory Agencies on the River (continued)

Extensions

1. Record water meter readings at the beginning of a day

and at the end of a day at home to check the accuracy

of water consumption figures used by water resources

agencies. Discuss why the home meter readings may

differ from the agency consumption figures.

2. Tour a water or wastewater treatment plant. If

possible, videotape or tape record the tour for later

reference. If the treatment plant needs upgrading to

meet EPA standards, how might this be accomplished?

3. Conduct a Delphi study, a technique used by some

regulatory agencies, to determine the consequences of

proposed water resources rules. A Delphi study

consists of the following steps:

• As a small group, brainstorm a list of the consequences

of one proposed water resources rule.

Devise a scale on which to rate the importance or

magnitude of each consequence.

• Determine the probability of each consequence

occurring.

• Calculate the overall effect of each consequence by

multiplying the importance rating by the probability

of occurrence.

• As a large group, discuss the overall effects of each

consequence and the reasoning used by each small

group in making a determination.

• Discuss the advantages and disadvantages of using

a Delphi study to consider the consequences of

proposed water resources regulations.

4. If it is not possible to visit regulators or others

associated with water resources use and regulation at

their place of work, invite them to visit the group.

Ask them to illustrate or demonstrate their work.

Persons to invite include: county health specialist,

county naturalist, county sanitarian, commercial

water quality tester, well driller. Discuss the water

resources regulations important in their jobs.

5. Take on the role of law makers. Write five rules to

protect water quality, or public health and safety

associated with water resources. Write to legislators

concerning the existence, future existence, or

nonexistence of the rules proposed.

Evaluation

1. Identify the area of geographical jurisdiction for at

least three government agencies charged with

safeguarding water quality.

2. Identify and explain the subjects of concern for at

least three government agencies charged with

safeguarding water quality in the local area.

3. Explain how citizens can have a role in the actions of

at least three water resources agencies.

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Appendices

Global Temperature

Data Set

• Glossary

• Evaluation Forms

• Image Applications

• Sources of Remote

Sensing Imagery

• Reading and Resources

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Global Temperature Data Set

These data are global average temperature anomalies (variations) from a global average temperature of 15˚C (59˚F) which

was calculated from a reference period of temperatures taken between 1950 and 1979 (the values listed are not corrected for

the influences of El Nino/Southern Oscillation (ENSO)). These data were compiled by PD Jones and TML Wigley of the

Climatic Research Unit at the University of East Anglia in England. For a comprehensive review of how the data were

gathered, and corrected for errors, read Jones & Wigley’s article in the August 1990 issue of Scientific American.

For more of the data in this set see: Jones, PD, TML Wigley, and KR Briffa. 1994. Global and hemispheric temperature

anomalies-land and marine instrumental records. pp. 603-608. In TA Boden, DP Kaiser, RJ Sepanski, and FW Stoss (eds.),

Trends ’93: A Compendium of Data on Global Change. ORNL.CDIAC-65. Carbon Dioxide Information Analysis Center,

Oak Ridge National Laboratory, Oak Ridge, Tenn., USA. To obtain data from CDIAC electronically contact the following

internet address: DCP@ORNL.GOV. Their homepage is http://cdiac.esd.ornl.gov:80/cdiac/

Year & Global Average Temperature Anomalies based on 1950-1979 Reference

GLOBAL

GLOBAL

GLOBAL

TEMPERATURE

TEMPERATURE

TEMPERATURE

YEAR

VARIATION

YEAR

VARIATION

YEAR

VARIATION

1854 -0.12

1855 -0.43

1856 -0.28

1857 -0.47

1858 -0.38

1859 -0.18

1860 -0.38

1861 -0.45

1862 -0.58

1863 -0.23

1864 -0.46

1865 -0.23

1866 -0.20

1867 -0.23

1868 -0.27

1869 -0.21

1870 -0.31

1871 -0.37

1872 -0.28

1873 -0.30

1874 -0.39

1875 -0.44

1876 -0.40

1877 -0.12

1878 0.02

1879 -0.35

1880 -0.32

1881 -0.29

1882 -0.30

1883 -0.35

1884 -0.44

1885 -0.38

1886 -0.27

1887 -0.40

1888 -0.31

1889 -0.17

1890 -0.40

1891 -0.34

1892 -0.38

1893 -0.43

1894 -0.35

1895 -0.31

1896 -0.14

1897 -0.10

1898 -0.31

1899 -0.18

1900 -0.05

1901 -0.14

1902 -0.25

1903 -0.38

1904 -0.47

1905 -0.31

1906 -0.22

1907 -0.41

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Global Temperature Data Set (continued)

GLOBAL

GLOBAL

GLOBAL

TEMPERATURE

TEMPERATURE

TEMPERATURE

YEAR

VARIATION

YEAR

VARIATION

YEAR

VARIATION

1908 -0.44

1909 -0.36

1910 -0.35

1911 -0.40

1912 -0.31

1913 -0.33

1914 -0.16

1915 -0.05

1916 -0.29

1917 -0.47

1918 -0.35

1919 -0.25

1920 -0.23

1921 -0.20

1922 -0.28

1923 -0.25

1924 -0.29

1925 -0.17

1926 0.00

1927 -0.13

1928 -0.14

1929 -0.32

1930 -0.14

1931 -0.04

1932 -0.11

1933 -0.22

1934 -0.11

1935 -0.16

1936 -0.13

1937 0.01

1938 0.08

1939 -0.03

1940 0.03

1941 0.04

1942 0.05

1943 0.00

1944 0.16

1945 0.05

1946 -0.06

1947 -0.04

1948 -0.05

1949 -0.08

1950 -0.14

1951 -0.02

1952 0.08

1953 0.13

1954 -0.11

1955 -0.14

1956 -0.22

1957 0.09

1958 0.11

1959 0.05

1960 -0.02

1961 0.12

1962 0.11

1963 0.13

1964 -0.18

1965 -0.12

1966 -0.04

1967 -0.01

1968 -0.06

1969 0.06

1970 0.05

1971 -0.08

1972 0.02

1973 0.14

1974 -0.10

1975 -0.09

1976 -0.22

1977 0.11

1978 0.04

1979 0.10

1980 0.19

1981 0.27

1982 0.09

1983 0.30

1984 0.12

1985 0.09

1986 0.17

1987 0.30

1988 0.34

1989 0.25

1990 0.39

1991 0.35

1992 0.17

1993 0.21

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Glossary

Acid Deposition

is precipitation (rain, snow, etc.) made acidic by the introduction of sulfur dioxide and nitrogen oxides into the atmosphere

as a result of fossil fuel burning. Automobile exhaust and emissions from coal-fired power plants are two of the

primary causes of acid deposition. In severe cases, acid precipitation kills fish and other aquatic life and damages and

destroys trees and crops. In some instances, it has rendered entire lakes and forests nearly lifeless.

Advection

the predominantly horizontal large-scale movement of air that causes changes in temperature or other physical properties.

In oceanography, advection is the horizontal or vertical flow of sea water as a current. ■

Aerial Photo

a 9" X 9" photograph taken vertically downward from the air on 10" roll film. Aerial photo images may be in the form of

paper prints or transparent film. ▲

Air Mass

a widespread body of the atmosphere that gains certain meteorological or polluted characteristics while set in one

location. The characteristics can change as it moves away. ■

Albedo

the fraction of the total solar radiation incident on a body that is reflected by it (i.e., reflected sunlight). ■

Analog

information stored and processed as signal intensity or other measurement of a continuous physical variable. Analog

information processing translates and represents slight increments in data easily and conveys information by relative

position without relying on the numeric value necessary to convey the same information digitally. For example, you can

tell time on an analog watch even if it has no numbers on the face and a thermometer that displays temperature using a

needle or liquid can indicate fractions of a degree, as well as provide information about relative warmth by the position of

the dial or height of the liquid. On the other hand, this continuous analog information is harder to copy, store, manipulate,

and reproduce dependably. Anyone who has listened to a copy of a copy of a copy of a cassette tape has first-hand

knowledge of analog information degradation. For this reason, much analog information (video, audio, or field and

laboratory measurements of temperature, pressure, voltage, radiation, etc.) is converted to its digital equivalent. (See also

Digital, Digitizer) ▲

Anthropogenic

man made. Usually used in the context of emissions that are produced as the result of human activities. ■

Atmosphere

the envelope of air surrounding the Earth and bound to it by the Earth’s gravitational attraction. Studies of the chemical

properties, dynamic motions, and physical processes of this system constitute the field of meteorology. ■

AVHR

Advanced Very High Resolution Radiometer - imagery produced by NOAA satellites. ▲

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Glossary (continued)

CAD

Computer Aided Design. CAD originated on larger, dedicated workstations and minicomputers and has now migrated to

microcomputers. In its simplest sense, CAD is used for computerized drafting. Many CAD systems also provide more

advanced features like solid modeling and simulation. ▲

Climate

the statistical collection and representation of the weather conditions for a specified area during a specified time interval,

usually decades, together with a description of the state of the external system or boundary conditions.

The properties that characterize the climate are thermal (temperatures of the surface air, water, land, and ice), kinetic

(wind and ocean currents, together with associated vertical motions and the motions of air masses, aqueous humidity,

cloudiness and cloud water content, ground-water, lakes, and water content of snow on land and sea ice), and static

(pressure and density of the atmosphere and ocean, composition of the dry air, salinity of the oceans, and the geometric

boundaries and physical constants of the system). These properties are interconnected by the various physical processes

such as precipitation, evapotranspiration, infrared radiation, convection, advection, and turbulence. ■

Cloud Albedo

reflectivity that varies from less than 10 to more than 90% of the insolation and depends on drop sizes, liquid water

content, water vapor content, thickness of the cloud, and the sun’s zenith angle. The smaller the drops and the greater the

liquid water content, the greater the cloud albedo, if all the other factors are the same. ■

Cloud Feedback

the coupling between cloudiness and surface air temperature in which a change in surface temperature could lead to a

change in clouds, which could then amplify or diminish the initial temperature perturbation. For example, an increase in

surface air temperature could increase the evaporation; this in turn might increase the extent of cloud cover. Increased

cloud cover would reduce the solar radiation reaching the Earth’s surface, thereby lowering the surface temperature. This

is an example of negative feedback and does not include the effects of longwave radiation or advection in the oceans

and the atmosphere, which must also be considered in the overall relationship of the climate system. ■

Cloud

a visible mass of condensed water vapor particles or ice suspended above the Earth’s surface. Clouds may be classified

on their visual appearance, height, or form. ■

Color Composite

as associated with Landsat, a 24.1 cm (9.5 in.) color transparency or print generated from black and white triplet sets

usually using multispectral scanner bands 4,5, and 7. The resulting colors are arbitrarily derived, hence the expression

“false color.” ●

Color-Infrared (CIR)

color-infrared images may be collected by an electronic scanner or a camera that uses special film. Infrared film records

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Glossary (continued)

the photographic infrared radiation just beyond the range of human vision as red. Normal red from the scene becomes

green, and green becomes blue. Normal blue in the scene is filtered out and is not recorded. Any physical or biological

damage to growing plants which begins to cause a deterioration in their vigor (their water and/or chlorophyll content)

causes a rapid decrease in their red reflectance. CIR photographs show these changes much sooner and more dramatically

than normal photographs or human eyesight. Healthy, green vegetation appears in bright red, while damaged, diseased, or

dying vegetation appears in shades of pink, tan, and yellow. This knowledge was first used in the Second World War

when color-infrared film was called camouflage detection film. It provided pre-visual detection of the changes in

vegetation cut or damaged by military activity and could very easily separate color-camouflage materials (like olivegreen

canvas) from live foliage. ▲

Convection

atmospheric or oceanic motions that are predominantly vertical and that result in vertical transport and mixing of

atmospheric or oceanic properties (i.e., heat and cold). Because the most striking meteorological features result if

atmospheric convective motion occurs in conjunction with the rising current of air (i.e., updrafts), convection is sometimes

used to imply only upward vertical motion. ■

Coregistration

the condition in which associated raster and/or vector objects overlay each other with correct orientation and geometry so

that corresponding internal features align. ▲

Data

a magnitude, figure or relation supposed to be given, drawn, or known in a mathematical investigation from which other

magnitudes, figures or relations are to be deduced. ❖

Digital

information stored and processed with numerical digits, often in base 2. Digital information processing is constrained by

the finite set of numbers a system uses, such that every data value is forced into its nearest representation. For example, a

digital temperature sign at the local bank has no way to deal with fractions of a degree: it can show 75° or 76°, but not 75

and 2/3°. At some point, every digital system faces the same kind of limit in accuracy. On the other hand, digital information

is easy to copy, store, manipulate, and reproduce dependably.

(See also Analog) ▲

Digitize

convert analog data into a digital form; also, more specifically, use a digitizing tablet to convert data to digital

form. ▲

Digitizer

a device that converts an analog signal or representation to a digital one. (See also Video Digitizing Board, X-Y Digitizing

Tablet, and Scanner) ▲

Electromagnetic Spectrum

“the entire spectrum, considered as a continuum of all kinds of electric, magnetic, and visible radiation, from gamma rays

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Glossary (continued)

having a wavelength of 0.001 angstrom to long waves having a wavelength of more than 1 million km” (Random House).

Remote sensing devices typically record electromagnetic bands in the region of optical light and may include the near

infrared. (See also Spectral Band) ▲

Evapotranspiration

discharge of water from the Earth’s surface to the atmosphere by evaporation from bodies of water, or other surfaces, and

by transpiration from plants.

False Color Composite

see color composite. ●

Frame Grabbing

Background: composite video and U.S. standard broadcasts repeat each field (see definition) every 1/60 of a second.

Two interlaced fields, each containing alternate lines of the image make up one video frame that lasts 1/30 of a second. A

video frame-grabber is a microcomputer interface board that accepts a video input signal and passes it to a color monitor.

A program signals the video frame-grabber to both freeze and digitize one video frame. Digitizing a video frame may

transform each picture element (Pixel) in the frame to a single byte in the board’s memory. More commonly, it simultaneously

captures, digitizes, and stores the video’s separate red, green, and blue color values. Some frame-grabbers can be

set to grab only a single field to avoid the relative movement between a frame’s two fields. If the video comes from a

camera that has high-speed electronic shuttering (like 1/1000 of a second), movement in the 1/30 of a second between the

primary field and the secondary field causes saw-toothed edges on alternate lines in straight features like road edges, and

vertical poles. (See also Video Digitizing Board) ▲

Frame or Video Frame

a complete video image which consists of two interlaced fields. Odd lines of the frame are contained in the primary field

which is alternated with the secondary field that contains the even lines. The primary field lasts 1/60 of a second in

standard broadcast video. The secondary field follows in the next 1/60 of a second. The entire frame takes 1/30 of a

second to display. There is a difference of 1/60 of a second between alternate lines in the image. ▲

Global Change

refers to environmental change caused by the aggregate of interactive linkages among major Earth systems — climate

and hydrologic systems, biogeochemical dynamics, ecological systems and dynamics, solid earth processes, solar

influences, and human interactions with these systems.

Global Warming

is a term used to describe the warming of Earth’s climate due to an increased Greenhouse Effect (see below) caused by

human beings introducing large amounts of carbon dioxide, methane, and other greenhouse gases into the atmosphere. It

is believed that Earth’s climate could warm as much as 5 ˚C (9 ˚F) as early as the middle of the next century—a rate of

climate change tens of times faster than the average rate of natural change.

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Glossary (continued)

Greenhouse Effect

is a phrase used to describe the increased warming of the Earth’s surface and lower atmosphere due to carbon dioxide and

other atmospheric gases that, like the glass panels in a greenhouse, let the sun’s energy in, but block the long wave

radiation emitted by the earth’s surface after being heated by the incoming solar energy. Were it not for the existence of

the Greenhouse Effect, Earth’s surface temperatures would be about 33 ˚C (60 ˚F) colder than they are and life as we

know it would not exist.

Ground Resolution

the limit of detail clarity in an image of the Earth’s surface collected by some remote sensing device, usually measured in

meters. An image with a ground resolution of 10 meters shows no ground features smaller than 10 X 10 meters. Each

data cell (or Pixel) in such an image contains one averaged value for a distinct 10 X 10 meter surface area. ▲

Ground Truth

information collected at the same site and at the same time that a remote sensing system collects data. Ground Truth data

are used to interpret and calibrate remotely sensed observations. ▲

Landsat

is the name given to a group of 5 satellites which collect remotely sensed data about Earth. Landsat 1, originally called

Earth Resources Technology Satellite or ERTS-1, was launched in 1972 to apply remote sensing techniques to the

inventory, monitoring, and management of Earth’s natural resources. There are currently two sensors for the Landsat

system — multispectral scanner (MSS) and thematic mapper (TM). The resolution of MSS data is 80 meters by 80

meters; it acquires black and white images in 4 spectral bands in the visible and near-infrared portions of the electromagnetic

spectrum. The resolution of TM is 30 meters by 30 meters with sensing in 7 spectral bands.

Longwave Radiation

the radiation emitted in the spectral wavelength greater than 4 angstrom corresponding to the radiation emitted from the

Earth and atmosphere. It is sometimes referred to as “terrestrial radiation” or “infrared radiation,” although somewhat

imprecisely. ■

Modeling

an investigative technique that uses a mathematical or physical representation of a system or theory that accounts for

some or all of its known properties. Models are often used to test the effects of changes of system components on the

overall performance of the system. ■

MSS

Multi-Spectral Scanner. A sensing device on the Landsat satellite that collects simultaneous images over multiple ranges

of the spectrum. MSS has a pixel resolution of 80 meters. ▲

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Glossary (continued)

Multiband or Multispectral

images optically acquired in more than one spectral or wavelength interval. Each individual image is usually of the

same physical area and scale, but of a different spectral band. The MSS and TM sensors aboard the Landsat satellite

both collect simultaneous multispectral images. The TM sensor scans and stores seven individual images in spectral

bands ranging from the blue wavelengths up to those in the thermal infrared. ▲

Multisensor Images

coregistered images with the same cell size collected by different sensing devices. For example, a 10-meter SPOT

panchromatic image can be coregistered with a resampled Landsat TM image so that their cells correctly match. This

combination is called a multisensor image. ▲

NAPP Airphotos

National Aerial Photography Program airphotos. USGS CIR high altitude airphotos. The NAPP series replaces the

NHAP series. (See also NHAP). ▲

NHAP Airphotos

National High Altitude Program. NHAP is underwritten by the USGS and provides a publicly available collection of

CIR airphotos covering the United States in print or transparency format. ▲

NOAA Satellite

refers to the National Oceanic and Atmospheric Administration’s TIROS Polar Orbiting satellite which obtains images

with the Advanced Very High Resolution Radiometer (AVHRR) or the GOES Geostationary satellite with the Visible-

Infrared Spin-Scan Radiometer (VISSR). These images, used for weather prediction and other purposes, are available

from NOAA.

Ozone Depletion

refers to the thinning of the stratospheric ozone layer which protects Earth and its inhabitants from excess ultraviolet

radiation from the sun. Human-made chemicals, chlorofluorocarbons or CFC’s, are primarily responsible for the ozone

depletion which is now proceeding at an alarming rate. Ozone concentrations over the U.S. may have fallen as much as

5% in the last decade and there is a measurable thinning of the ozone layer over both poles, particularly over the South

Pole in the early Spring. (The issue of stratospheric ozone depletion is not to be confused with the problem of ground

level or tropospheric ozone which is a pollutant in the lower atmosphere.)

Panchromatic Image

an image collected in the broad visual wavelength range, but rendered in black and white. The term has historically

referred to a black and white photograph of a color scene. Since the SPOT satellite 10-meter images are collected over

this broad visual spectral band and are usually rendered in black and white, these images are called panchromatic ▲

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Glossary (continued)

Pixel or Picture Element

refers to a single sample of data in a digital image. The word pixel is a contraction of “picture element.”

Pollution

harmful substances deposited in the air, land or water, leading to a state of dirtiness, impurity, unhealthiness, or hazard. ✱

Precipitation

any or all forms of liquid or solid water particles that fall from the atmosphere and reach the Earth’s surface. It includes

drizzle, rain, snow, snow pellets, snow grains, ice crystals, ice pellets, and hail. The ratio of precipitation to evaporation is

the most important factor in the distribution of vegetation zones. Precipitation is also defined as a measure of the quantity,

expressed in centimeters or milliliters of liquid water depth, of the water substance that has fallen at a given location in a

specified amount of time. ■

Range

the space or extent included, covered, or used. ❖

Raster Cell

one value in a raster that corresponds to a specific area on the ground. A raster cell value may be the elevation above sea

level at one position in a survey site or the intensity of red radiation for a pixel in a video image. For convenience, a raster

is usually thought of as square or rectangular, although many image collection devices actually measure circular or

elliptical areas. ▲

Raster

a single, related, two-dimensionally grouped, set of numbers of a single data type. Each number represents the value of

some parameter. Its position in the group represents its relative position to the other values ▲

Remote Sensing

acquisition of information about objects or phenomena on the Earth (including land, oceans, and atmosphere) through the

use of sensory devices at positions separated from (remotely situated) the subject under study. Examples of remote sensors

include aircraft, satellites, and human eyesight, hearing, and smell. Obtaining information from a distance. ●

Resolution

the level of object detail or sharpness determined by how many picture elements (Pixels) compose an area of a display or

corresponding raster. Resolution may refer to sensors, raster objects, or displays. Low resolution display devices produce

images with a grainy visual texture. High resolution display use such small picture elements (Pixels) that they can produce

a near-photographic quality image. (See also Ground Resolution) ▲

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Glossary (continued)

Riparian

located or living along or near a stream, river, or body of water.

Satellites

here referring to human-made objects that orbit celestial bodies. In the Ground Truth Studies Project, we will be primarily

concerned with those that orbit the Earth and collect remotely sensed data of Earth’s surface. These include: Landsat

(MSS and TM), SPOT, and NOAA.

Scale

an indication of the relationship between the distances on a map, chart, or image and the corresponding actual distances.

Scanner

a digitizer that produces an image (raster object) from flat input material such as photographs, maps, and

drawings. ▲

Spectral Band or Spectral Region

a well-defined, continuous wavelength range in the spectrum of reflected or radiated electromagnetic energy. Red, green,

and blue are each spectral regions within the small portion of the spectrum that is visible to humans as light. Colorinfrared

images are composed of red, green, and a spectral region commonly called the photo infrared, which is not in the

visible portion of the electromagnetic spectrum. (See also Electromagnetic Spectrum, Color-Infrared) ▲

SPOT

the French Satellite Pour l’Observation de la Terre. There are two SPOT satellites: one collects images with 10-meter

ground resolution in a single panchromatic spectral region; the other collects 20-meter images in the three spectral

regions used for color-infrared maps. SPOT satellites may be pointed at an angle off-axis or off-nadir to collect forward

and rearward images: a techniques that yields stereoscopic image pairs from which accurate elevation rasters can be

computed. ▲

TM

Thematic Mapper. A sensing device on the Landsat satellite that scans and stores 7 individual images in spectral bands

ranging from the blue wavelengths up to those in the thermal infrared. TM has a pixel resolution of about 30 meters. ▲

Topographic Map

a map that uses colors and symbolic patterns to represent the general surface features of the Earth, such as grassland,

forest, marsh, agricultural, urban, and barren rock. ▲

Topography

the features of the actual surface of the Earth, considered collectively according to their form (grassland, cultivated,

desert, forest, swamp, etc.) A single feature, such as one mountain or one valley, is called a topographic feature. ▲

Transpiration

the process in plants by which water is taken up by the roots and released as water vapor by the leaves. The term can also

be applied to the quantity of water thus dissipated. ■

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Glossary (continued)

Turbid

opaque with suspended matter, such as of a sediment-laden stream flowing into a lake. ●

USGS

United States Geological Survey. ▲

Vector

a data structure for representing point and line data by means of 2- or 3-dimensional geometric (Cartesian x, y or x, y, z)

coordinates. In connection with GIS and computer graphics, “vector” can refer to a set of line segments joined end to end

to make a curved line in space. ▲

Verification

is establishing the accuracy of data by checking it against an independent means of collecting information; confirmation,

validation. Often ground truth observations and measurements are verification for remotely sensed data.

Video Digitizing Board

a video interface circuit board that samples or frame-grabs a video frame and constructs a digital image. Video digitizing

boards are slower than video capture boards, but can be used for non-standard, higher resolution video sources. (See also

Frame-Grabbing) ▲

Watershed Seed Point

the point at the base of a watershed into which all points in the watershed drain; often taken as the mouth of a stream or

river. ▲

Watershed

the entire area above a given point (called the watershed “seed”) that drains into that point. ▲

X-Y Digitizing Table

a peripheral device for manually translating line and point data (like engineering and technical drawings) into some

computer format (usually vector or CAD). The drawing is secured to the tablet, and the operator positions the device’s

cursor (which may look like a pen or a computer mouse with a crosshair lens) over lines and other elements, clicking a

button or pressing a key to record a coordinate. ▲

■ Glossary: Carbon Dioxide and Climate, ORNL/CDIAC-39, Oak Ridge National Library, Oak Ridge, Tennessee (1990)

● Glossary of Technical Terms, Mission to Earth: Landsat Views the World. Scientific and Technical Information

Office, National Aeronautics and Space Administration, Washington, D.C. (1976 and 1978)

▲ Glossary, A Guide to Map and Image Processing, MicroImages, Inc., Lincoln, Nebraska (1991)

✱ Glossary, Project WILD: Secondary Activity Guide, Project WILD, Boulder, Colorado (1983)

❖ Webster’s Third New International Dictionary, G. & C. Merriam Company, Publishers, Springfield,

Massachusetts (1971)

Uncited definitions by Aspen Global Change Institute.

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Glossary (continued)

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Image Application Chart

Image Application Chart

Soils and Land Use information to use as environmental education content

_________________________________________________________________________________________________________________________________________________________

Airplane platform Satellite platform

_________________________________________________________________________________________________________________________________________________________

Inventory Identify beach cliff erosion, landslides on hillsides and Map large-scale degradation

and mapping ground displacements Space shuttle imaging radar maps ancient drainage patterns

of resources Map soil units and delineate soil boundaries and potential present-day sources of near-surface water

Map land use and land use intensities Classify dune fields and identify rock types

Map annual extent of fires

Map faults and folds

_________________________________________________________________________________________________________________________________________________________

Quantifying Determine soil temperature with thermal infrared LANDSAT indicates extent of area burned by fire

the environment images ERTS assists soil temperature measurement

Delineate extent of erosion, desertification, and

encroachment of sand

Indicate land potential

Measure soil moisture

_________________________________________________________________________________________________________________________________________________________

Describe Suggest the design of rural access networks LANDSAT 5 and 6 TM provide soil moisture data for more

flow of matter Study dynamics of soil salinization intensive development such as resettlement

and energy EOS detects tectonic plate motion

Space shuttle detects dust storms in arid lands

_________________________________________________________________________________________________________________________________________________________

Evaluate change Record sequential land use as with gravel pits Document large-scale degradation: wind erosion,

and alternate Indicate amount of replacement of one land use salinization, and flooding

solutions for by another Monitor surface mining and reclamation

management of Compare the relative productivity of various LANDSAT TM indicates conversion of forest to cropland

ecosystems combinations of crop and grazing land LANDSAT updates knowledge of gross land-use changes

Record changes during the year because of tillage,

crop rotation, crop growth, and conservation measures

_________________________________________________________________________________________________________________________________________________________

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Image Application Chart (continued)

Aquatic Ecosystems information to use as environmental education content

_________________________________________________________________________________________________________________________________________________________

Airplane platform Satellite platform

_________________________________________________________________________________________________________________________________________________________

Inventory and Map watersheds, surface water bodies, water tempera- ERTS watershed, floodplain, wetlands, and inundation

mapping ture distributions and coastal features and reefs mapping

of resources Detect and map wetlands and floodplains Meteorological satellite cloud type identification

Identify potential recharge zones for groundwater Map the circulation patterns in large water bodies and

Identify hazardous substances in water the spread of phreatophytes in intermittent streams

Identify and map aquatic vegetation Inventory sewage and industrial outfalls

_________________________________________________________________________________________________________________________________________________________

Quantifying Estimate wetlands biomass LANDSAT wetland biomass estimation and coastal primary

the environment Indicate extent of floods or snow cover productivity measurement

Indicate extent of lake eutrophication Meteorological satellite indicates amount of cloud cover

Measure snow depth and sea-surface temperature

Measure stream length and channel development Measure extent and character of sea-ice

Measure sea-surface wind direction and velocity Estimate oceanic biologic activity

_________________________________________________________________________________________________________________________________________________________

Describe Study turbidity, transparency, thermal stratification ERTS assists water quality assessment with data about

flow of and surface thermal patterns water depth variations, sediments, and pollution

matter and investigate pollution concentrations concentrations

energy assess ocean wave pattern and size detect ice flows

detect freshwater upwellings in coastal zones assess amount, direction, and movement rate of floating

and current patterns algae, foam, and suspended matter in coastal morphology

study ocean currents with thermal scanning

_________________________________________________________________________________________________________________________________________________________

Evaluate monitor biological and chemical changes in waters

change and used LANDSAT documents drainage, reclamation, and

alternate predict and monitor floods polderizaton of land

solutions for monitor seasonal extent of change in surface water LANDSAT monitors chlorophyll, particulate, and suspended

management of coverage, aquatic vegetation abundance, and solids in aquatic environs

ecosystems degree of turbidity LANDSAT detects oil slicks and seepage in coastal areas

monitor the impact of large impoundments determine coastline erosion or accretion

_________________________________________________________________________________________________________________________________________________________

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Image Application Chart (continued)

Wildlife information to use as environmental education content

_________________________________________________________________________________________________________________________________________________________

Airplane platform Satellite platform

_________________________________________________________________________________________________________________________________________________________

Inventory locate grazing animals LANDSAT MSS mapping of woody country preferred by grey

and mapping map migration and nomadic movements kangaroos

of resources map forage vegetation and damage by locate the conditions for locust outbreaks

animals ERTS characterization of staging and resting

thermal location of animals at night

zoophenological mapping

_________________________________________________________________________________________________________________________________________________________

Quantifying create permanent records for later analysis and LANDSAT MSS estimate of Australian grey kangaroos

the environment counting observe North Sea seals and Australian dugong

determine number and status of grazers

census wild and domestic species such as Beluga

whales, snow, blue, and Canada geese, nesting

pairs of gannets, kulan, caribou, and seabirds

_________________________________________________________________________________________________________________________________________________________

Describe follow migratory herds and nomads track locust swarms

flow of correlate macro, meso, and micro events affecting track dugong off Australian coast

matter and animal distribution

energy determine distribution of animals during migration

and after calving

_________________________________________________________________________________________________________________________________________________________

Evaluate evaluate and monitor animal or wildfowl habitat ERTS evaluation of fish schools

change and detect changes in the numbers or seasonal and longeralternate

term distribution

solutions for check the efficacy of management strategies and

management of policies

ecosystems

_________________________________________________________________________________________________________________________________________________________

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Image Application Chart (continued)

Population Ecology principles that may be illustrated with remotely sensed images

____________________________________________________________________________________________________________

Ecologic Principle General description of Specific images recommended

remotely sensed image to use in particular biosphere reserves

____________________________________________________________________________________________________________

age structure photo showing how a group of organisms is divided photo of an elephant herd or of a timber plantation

into individuals at different stages in the life cycle

____________________________________________________________________________________________________________

density aerial photo recording the random, uniform, or color aerial photo of flamingos in tidal marsh, whales

clumped distribution of a population within a unit in shallow water, or mopane trees on the African

of space savanna

____________________________________________________________________________________________________________

ecological niche color photo documenting an animal’s profession, what photo series of warbler species feeding in each one’s

it does region of a tree

____________________________________________________________________________________________________________

habitat aerial photo of mountain showing zones of vegetation color aerial photo of mountain valley showing

varying with altitude hardwoods at warmer lower elevations and confers at

cooler higher elevations

____________________________________________________________________________________________________________

predation color photo of predator eating prey photo of lions eating a wildebeest

____________________________________________________________________________________________________________

migration color photo of seasonal movement of groups of animals aerial photo of caribou moving north across the tundra

in spring

____________________________________________________________________________________________________________

intraspecific photo of an animal marking its territory color photo of male red-winged blackbirds perched on

competition vegetation in the center of each one’s nesting territory

____________________________________________________________________________________________________________

interspecific aerial photo demonstrating that two species are seeking aerial black and white photo of aromatic shrubs invading

competition the same resource annual grassland by exuding biochemical inhibitors

____________________________________________________________________________________________________________

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Image Application Chart (continued)

Community Ecology principles that may be illustrated with remotely sensed images

_________________________________________________________________________________________________________________________________________________________

Ecologic principle General description of Specific images recommended in

remotely sensed image to use particular biosphere reserves

_________________________________________________________________________________________________________________________________________________________

ecotone photo of area where two major communities meet and black and white or color photo of western coniferous

blend together forests meeting short grass prairie in mountain foothills

_________________________________________________________________________________________________________________________________________________________

primary succession image showing the initial establishment and development aerial photo series showing lichens spreading over a

of an ecosystem rock surface

_________________________________________________________________________________________________________________________________________________________

secondary succession images depicting re-establishment of an ecosystem aerial photo series of eutrophying lake showing

image of one community giving way to another yearly successional stages in center with open water

and widening later successional stages at the

shoreline

_________________________________________________________________________________________________________________________________________________________

human communities aerial photos of different kinds of dwelling arrangements aerial photo of the bhoma of Sahelian pastoralists, the

and their surroundings village among Javanese sawah fields, or a hamlet in

the Himalayas

_________________________________________________________________________________________________________________________________________________________

microenvironment close-up of a localized distribution of organisms photo of a hemlock stand within an oak-maple forest or

within a community because of micro-differences of sedges and frogs in a prairie pothole in spring

in moisture, light, or other factors

_________________________________________________________________________________________________________________________________________________________

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Image Application Chart (continued)

Ecosystem Ecology principles that may be illustrated with remotely sensed images

_________________________________________________________________________________________________________________________________________________________

Ecologic Principle General description of Specific images recommended in

remotely sensed image to use particular biosphere reserves

_________________________________________________________________________________________________________________________________________________________

energy flow thermal image recording a temperature gradient aerial thermal infrared image of water surface

temperature in an estuary

_________________________________________________________________________________________________________________________________________________________

materials flow image series showing the movement of matter satellite color photos of ocean eddies

_________________________________________________________________________________________________________________________________________________________

productivity image series documenting the amount of increase of satellite infrared images of the greening of arid

organic matter per unit of time lands after the rainy season

_________________________________________________________________________________________________________________________________________________________

biome images distinguishing dominant vegetation types in aerial photos or satellite infrared images

different places recording the vegetation of the tundra,

temperate deciduous forests, or Mediterranean

scrub

_________________________________________________________________________________________________________________________________________________________

systems analysis satellite images of global patterns color photo of the Earth from Skylab

_________________________________________________________________________________________________________________________________________________________

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Sources for Remote Sensing Imagery

As a service for participating teachers, AGCI will provide assistance and centralized ordering.

To order images directly, contact the resources listed below.

Topographic Maps

Topographic maps are also available from local hiking/camping/outfitting shops.

order from:

Map Distribution, USGS

Box 25286

Federal Center,

Denver, CO 80225

allow 2 weeks cost: $2.50 each

Map Express

P.O. Box 280445,

Lakewood, CO, 80228

1-800-MAP-0039

same day service cost: $4.50 each

Aerial Photographs ❖

Government Sources, United States

Nearly every federal agency involved with land preservation, planning, or management maintains collections of aerial

photographs that span the nation from picture-perfect coast to picture-perfect coast.

U.S. Geological Survey, Aerial Photography Summary Record System, established in 1976 as the first Earth Science

Information Center data base, catalogs the in-progress and completed aerial photographs for the U.S. to assist in locating

a desired photograph. The USGS, through its ESIC offices, can sell prints from photography from a number of federal

agencies, such as the Bureau of Reclamation, the U.S. Navy, and the Environmental Protection Agency. A pamphlet,

How to Obtain Aerial Photographs, available from the USGS, may be helpful in obtaining aerial photos( User Services

Section, EROS Data Center, U.S. Geological Survey, Sioux Falls, SD 57198; 605-594-6151) or (Earth Science Information

Center, 507 National Center, 12201 Sunrise Valley Dr., Reston, VA 22092; 703-860-6045).

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Sources for Remote Sensing Imagery (continued)

U.S. Department of Agriculture, Aerial Photography Field Office in Salt Lake City, part of the Agricultural Stabilization

and Conservation Service (Aerial Photography Field Office, P.O. Box 30010, Salt Lake City, UT 84130; 801-524-

5856), has thousands of aerial photographs covering most of the nation’s major cropland. USDA’s National Forest

Service has aerial photographs of the nation’s forests.

Department of Commerce, National Ocean Service (Distribution Branch, (N/CG33), National Ocean Service, Riverdale,

MD 20737; 301-436-6990) has aerial photographs of the nation’s coastline.

Landsat Images ❖

Landsat images are available for the 50 states and for most of the Earth’s land surface outside the U.S. There are several

products available for any given location, including:

• Single black-and-white images, available as film negatives, film positives, or paper prints.

• Complete sets of four black-and-white images and a false-color composite.

All false-color composites are available as film positives or paper prints.

• Computer tapes containing digital data.

Each Landsat image covers about 8 million acres. Images do not reveal outlines of small areas, like houses or small

towns and villages, but provide views of broad areas and large features, such as mountain ranges and the outlines of

major cities.

Landsat images within the past two years (very expensive— $2,750) are available through EOSAT offices located at the

EROS Data Center (USGS-Department of Interior, EROS Data Center, Sioux Falls, SD, 57198;

605-594-6151), where orders are processed. For images over two years old (much cheaper - $200), order directly from

EROS. When ordering, it is important to describe the exact area in which you are interested, including, if possible, the

geographic coordinates or a map marked with the specific area. You should also indicate:

• The type of product (black-and-white, false-color, or digital tape);

• The minimum image quality acceptable;

• The maximum percent of acceptable cloud cover (10 percent to 90 percent); and

• The preferred time of the year.

A useful brochure, “Landsat Products and Services” is available from the EROS Data Center. This brochure includes a

price list, order form, inquiry form, reference aids, and other information. To order specific images of the 48 contiguous

United States, you can use the form Selected Landsat Coverage (NOAA Form 34-1205, available free from EROS and

USGS Earth Science Information Centers), which includes a map of the U.S. showing the locations of individual Landsat

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Sources for Remote Sensing Imagery (continued)

images selected for their clarity and lack of cloud cover. USGS has also prepared a number of photomaps, mosaics, and

other images produced from Landsat, SPOT, and other imagery, including an impressive view of the entire U.S. Prices

for most of these range from $2.50 to $6, not including postage and handling charges for mail orders.

SPOT Images ❖

SPOT’s images may be obtained directly from SPOT Image Corp. (1897 Preston White Drive, Reston, VA 22091; 703-

620-2200), the wholly-owned subsidiary of the French company created to market SPOT’s services. SPOT data are

available as digital information in computer-compatible tapes and as black-and-white or color prints and transparencies.

Prices depend on several factors, including which of the three types of radiation that SPOT records (two bands of visible

light and one of near-infrared radiation) is desired, resolution quality (either 20-meter resolution or the sharper 10-meter

resolution), and the size of the print or transparency. For example, a 9 1/2" square black-and-white transparency

showing all three bands at a scale of 1:400,000 and 10-meter resolution is $2,450 - a color transparency at a scale of

1:400,000 (corrected for distortion to the point that it can be used to overlay on a printed map with high accuracy) and

20-meter resolution is $1,300. Prints are a bit less pricey ($250 each, black-and-white or color), but must accompany a

tape or transparency order. At such prices, SPOT images, however spectacular, are not intended for mere decoration.

Satellite-Image Maps ❖

USGS has published satellite-image maps for selected areas in the U.S. and such areas as Antarctica, the Bahamas, and

Iceland from multispectral (MSS) scanner, thematic mapper (TM), and SPOT imagery. Most of these image maps are

printed in false-color infrared. Notable examples are “Denali National Park, Alaska,” at a scale of 1:250,000 with a

standard topographic map on the reverse side ($7); “Washington, D.C.” at a 1:50,000 scale ($5.50); and “Point Loma,

California,” at a scale of 1:24,000 with a standard quadrangle map on the reverse side ($4). An order form listing these

maps is available from USGS ESIC offices nationwide or from the Distribution Center in Denver, Colorado (Denver-

ESIC 169 Federal Bldg., 1961 Stout Street, Denver, CO 80294; 303-844-4169 to order or for local office address and

phone #).

NOAA Images

Advanced Very High Resolution Radiometer (AVHRR) images ($20-$100), including mosaics of the United States,

hurricanes, and selected international locations, from NOAA weather satellites are available from the EROS Data Center

(USGS-Department of Interior, EROS Data Center, Sioux Falls, SD, 57198; 605-594-6151).

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Sources for Remote Sensing Imagery (continued)

Commercial Sources ❖

Geoscience Resources (2990 Anthony Road, P.O. Box 2096, Burlington, NC 27216; 919-227-8300; 800-742-2677)

distributes many USGS satellite-image maps, many with topographic maps on the reverse side. Most titles it distributes

portray areas of geological interest.

National Air Survey Center Corp. (4321 Baltimore Ave., Bladensburg, MD 20710; 301-927-7177) sells a variety of

satellite photography including mosaics of U.S. states, many cities, and several countries. Prices range from $25 to $250

for color prints, and $60 to $350 for color transparencies. A brochure, “Satellite Photography - Space Portrait USA,” is

available.

Spaceshots Inc. (11111 Santa Monica Blvd., Ste. 210, Los Angeles, CA 90025; 310-792-5692; 800-272-2779) produces

prints of satellite images of the Earth. More than 20 images are available for areas in North America. Print size and area

covered varies; prints are available on paper or laminated; prices range from $12.95 to $21.95.

❖ The Map Catalog, Second Edition, A Tilden Press Book, Vintage Books, A division of Random House, Inc., New

York, NY (1990).

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Suggested Reading and Resources

Internet Homepages

A partial list of Internet Homepages with information about global change.

Aspen Global Change Institute (AGCI)

http://www.agci.org

AGCI global change science and education programs

U.S. Global Change Research Information Office (GCRIO)

http://www.gcrio.org/

access to global change data and information

NASA SpaceLink

http://spacelink.msfc.nasa.gov/

access to NASAs educational programs and information

Carbon Dioxide Information Analysis Center (CDIAC),

http://cdiac.esd.ornl.gov:80/cdiac/

global change data sets and information

The GLOBE Program

http://www.globe.gov

international education program of student environmental data

Global Warming

“The Changing Climate,” by Stephen Schneider, Scientific American, September 1989 (9). pp. 70-79.

“Endless Summer: Living with the Greenhouse Effect,” Discover, October, 1988.

Global Climatic Change,” by R. A. Houghton and G. M. Woodwell, Scientific American,

April 1989 Volume 260 (4).

Global Warming,” 4-page pamphlet, 1989, printed and distributed by: The Sierra Club, Public Affairs, 730 Polk Street,

San Francisco, CA 94109.

Global Warming Trends,” Phillip D. Jones and Tom M. L. Wigley, Scientific American, August 1990, pp. 84-91.

“The Great Climate Debate,” by Robert M. White, Scientific American, July 1990, pp. 36-43.

The Climate Crisis: Greenhouse Effect and Ozone Layer, John Becklane and Franklin Watts, New York, London,

Toronto, Sydney, 1989.

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Suggested Reading and Resources (continued)

CO 2

Diet for a Greenhouse Planet: A Citizen’s Guide for Slowing Global Warming, DeCicco, John, Audubon Policy

Reports 1990. 75 p.

The Co-Evolution of Climate and Life, Schneider, Stephen and Londer, Randi S., Sierra Club Books, San Francisco, CA

1984. 563 p.

Global Climate Change and Life on Earth, Wyman, Richard L., editor, Routledge, Chapman and Hall, New York, NY,

1991. 282 p.

Global Climate Change: Human and Natural Influences, Singer, S. Fred, editor, Paragon House Publishers, New York,

NY 1989. 424 p.

Global Warming and The Greenhouse Effect: Teacher’s Guide (grades 7-10), Hocking, Colin, et. al., Great Explorations

in Math and Science (GEMS), Lawrence Hall of Science, University of California at Berkeley, Berkeley, CA 1990.

Global Warming: Are We Entering the Greenhouse Century?, Schneider, Stephen H., Sierra Club Books, Random House

1989. 317 p.

Global Warming, Assessing the Greenhouse Threat, Pringle, Laurence, Arcade Publishing: Little, Brown and Company,

New York, NY, 1990.

The Greenhouse Effect, Hare, Tony (part of the “Save Our Earth” series), Gloucester Press, New York, London, Toronto,

Sydney, 1990.

The Greenhouse Effect: Life on a Warmer Planet, Johnson, Rebecca L., Lerner Publications Company, Minneapolis, MN,

1990.

Our Global Greenhouse, April Koral and Franklin Watts, New York, London, Toronto, Sydney, 1989.

Potential Effects of Global Climate Change on the United States, Smith, Joel B. and Tirpak, Dennis A., editors, Hemisphere

Publishing Corporation, New York, NY 1990. 689 p.

Population Growth

“The Growing Human Population,” by N. Keyfitz, Scientific American 261(3):119-126, September 1989.

The Population Explosion, Ehrlich, Paul R. and Anne H., Simon and Schuster,

New York, NY (1990). 320 p.

Ozone Depletion

“Ozone Breakdown,” by Michael D. Lemonick, Time Magazine, February 17, 1992, pp. 60-68.

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Suggested Reading and Resources (continued)

Ominous Future Under the Ozone Hole: Assessing Biological Impacts in Antarctica, Voytek, Mary A., Environmental

Defense Fund, Wildlife Program, Washington, DC (1989). 69 p.

Ozone Diplomacy: New Directions in Safeguarding the Planet, Benedick, Richard Elliot,

Harvard University Press, Cambridge, MA (1991). 300 p.

The Ozone Hole: A Selected Bibliography, Lockerby, Robert W., Vance Bibliographies,

Monticello, IL (1989). 12 p.

Biological Diversity

Keeping Options Alive: The Scientific Basis for Conserving Biodiversity, Reid, Walter V. and Miller, Kenton R., World

Resources Institute, Washington, DC (1989). 128 p.

Lessons from the Rainforest: Essays by Norman Myers, Randall Hayes, Francis Moore Lappé, and others, Head, Suzanne

and Heinzman, Robert, editors, Sierra Club Books, San Francisco, CA 1990.

National Forum on Biodiversity, Wilson, E. O. editor, National Academy Press,

Washington, DC (1988). 521 p.

Remote Sensing

A Guide to Remote Sensing: Interpreting Images of the Earth, Drury, S. A.,

Oxford University Press, 1990. 199 p.

Educators Guide for Mission to Earth: Landsat Views the World, Tindal, Margaret A., Goddard Space Flight Center 1978.

58 p.

Exploring Earth From Space, Erickson, Jon, Blue Ridge Summit: TAB Books 1989. 192 p.

The Home Planet, Kelley, Kevin W., Addison-Wesley Publishing Company, New York, NY (1988). 176 p.

Introduction to Remote Sensing, Campbell, James B., Guilford Press 1987. 551 p.

The Map Catalog: Every Kind of Map and Chart on Earth and Even Some Above It, Makower, Joel, editor., (2nd ed.)

Tilden Press 1990. 364 p.

Mission to Earth: Landsat Views the World, Short, Nicholas M. II.,

U.S. Government Printing Office 1976. 459 p.

Principles of Remote Sensing, Curran, Paul J., Longman 1985. 282 p.

© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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Suggested Reading and Resources (continued)

Remote Sensing and Image Interpretation, Lillesand, Thomas M. & Ralph Kiefer., (2nd ed.)

Wiley 1987. 721 p.

Remote Sensing: Methods and Applications Hord, R. Michael, Wiley 1986. 362 p.

Remote Sensing: Principles and Interpretation, Sabins, Floyd F., (2nd ed.) Freeman 1987. 449 p.

General/Comprehensive

“Managing Planet Earth,” Scientific American, Volume 261, Number 3, September, 1989.

Earth in the Balance, Gore, Senator Al, Houghton Mifflin Company, Boston,

New York, London (1992). 407 p.

50 Simple Things You Can Do to Save the Earth, EarthWorks Group.

EarthWorks Press, Berkeley, CA (1989).

One Earth, One Future: Our Changing Global Environment, Silver, Cheryl Simon, National Academy Press, Washington,

DC 1990. 196 p.

State of the World 1984-1992, (published each year) Brown, Lester R. et. al., W. W. Norton & Company, New York,

London.

Videotapes

Should We Believe Climate Prediction? Presented by Dr. Richard Somerville at the Scripps Institution of Oceanography.

Distributed by Aspen Global Change Institute.

An Introduction to Remote Sensing, (Presented by Ed Sheffner - NASA/AMES TGS Technologies), distributed by

Aspen Global Change Institute (100 East Francis, Aspen, CO 81611; 303-925-7376).

Our Planet Earth, Bullfrog Films, Inc. (P.O. Box 149, Oley, PA 19547; 800-543-FROG or 215-779-8226).

The Films of Charles & Ray Eames, Volume 1, Powers of Ten, Pyramid Film & Video (2801 Colorado Avenue, Santa

Monica, CA 90404; 800-421-2304).

Spaceship Earth: Our Global Environment, WorldLink (3629 Sacramento Street, San Francisco, CA 94118).

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© ASPEN GLOBAL CHANGE INSTITUTE 1995 GROUND TRUTH STUDIES

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